CITY  OF  NEW  YORK 

THE  AQUEDUCT  COMMISSIONERS. 


REPORT  OF  THE  RESULTS 


EXPERIMENTS  AT 

JEROME  PARK  RESERVOIR 

TO  DETERMINE 

THE  LAWS  OF  PROPORTIONING  CONCRETE. 


MADE  BY  AUTHORITY  OF  THE  AQUEDUCT  COMMISSIONERS, 
UNDER  THE  DIRECTION  OF  THE  CHIEF  ENGINEER. 


BY 


WM.  B.  FULLER, 

MEMBER  AMERICAN  SOCIETY  OF  CIVIL  ENGINEERS. 


Evening  lpost  3ob  (printing  ©ffice, 
mew  H?orft. 


TABLE  OF  CONTENTS- 


PAGE 


Conclusions  from  Tests .  4 

Further  Tests  Suggested  and  Enumerated .  8 

Description  of  Tests .  10 

Mechanical  Analysis .  13 

Sieves  and  Other  Apparatus .  13 

Plotting  Analysis  Curves .  15 

Preparation  of  Materials .  16 

Cement .  16 

Purity  Test  of  Cement .  17 

Aggregate  .  17 

Character  and  Composition  of  Jerome  Park  Rock .  18 

Uselessness  of  Determination  of  Voids  in  Sand .  20 

Screening  Aggregate  in  Laboratory .  20 

Diameters  of  Aggregate .  22 

Methods  and  Apparatus  for  Determining  Density . 23 

Weighing .  23 

Measuring .  23 

Mixing . . .  25 

Ramming .  26 

Removing  Surplus  Water .  26 

Final  weighing .  26 

Measurement . .  .  28 

Recording  and  Computing  Data .  28 

Proportioning  the  Ingredients  for  Maximum  Density .  30 

Necessity  for  Using  Cement  in  Density  Tests .  31 

Density  Tests  with  2 14-Inch  Jerome  Park  Stone .  32 

Density  Tests  with  1-Inch  and  %-Inch  Stone .  33 

Cement  vs.  Fine  Sand .  35 

Density  Tests  with  Cowe  Bay  Material .  35 

Ideal  Sand .  36 

Equations  of  Ideal  Mechanical  Analysis  Curves .  36 

Directions  for  Plotting  Ellipses .  37 

Diagram  of  Ideal  Curves .  37 

Methods  and  Apparatus  for  Beams .  38 

Weighing .  38 

Mixing .  38 

Consistency .  38 

Marks  for  Specimens .  39 

Placing  in  Molds .  39 

Recording  and  Computing  Data  on  Beams . 40 

Beam  Testing  Machine .  41 

Compression  Pieces . 42 

Compressive  Strength  of  True  Prisms  vs.  Capped  Pieces  of  Beams  ....  43 

1904  Beam  Tests .  44 

1905  Beam  Tests .  44 

Methods  of  Preparing  Materials  for  Natural  Proportions .  47 

Mechanical  Analysis  Curves  Used  in  Beam  Tests .  48 

Equations  of  Mechanical  Analysis  Curves  for  Artificial  Propor¬ 
tioning  of  Aggregates  and  Cement . . . 57 

Comparative  Tests  Forming  Basis  of  Conclusions .  57 

Aggregates  of  Different  Maximum  Size,  Comparative  Density  and 

Strength .  57 


I 


0 


IV 


PAGE 

Jerome  Park  vs.  Cowe  Bay  vs.  Mixed  Aggregates,  Comparative  Density 

and  Strength .  59 

Graded  Aggregate  vs.  Mixtures  in  Ordinary  Proportions,  Compara¬ 
tive  Density  and  Strength .  63 

Graded  Coarse  Aggregate  vs.  Uniform  Size,  Comparative  Density  and 

Strength .  63 

Influence  of  the  Analysis  of  the  Coarse  Aggregate  upon  the 

Strength  of  the  Concrete .  66 

Effect  of  Fineness  of  Sand  upon  Density  and  Strength .  67 

Relation  of  Ideal  Curves  of  Different  Size  Stone .  67 

Effect  on  Density  and  Strength  of  Concrete  by  Increasing  Percent¬ 
age  of  Sand  and  Decreasing  Stone .  68 

Proportioning  Sand  and  Stone  in  Practice .  69 

Concrete  with  Different  Percentages  of  Cement,  Comparative  Den¬ 
sity  and  Strength .  69 

Effect  upon  Density  of  Substituting  Cement  for  Fine  Sand .  70 

Complete  Schedule  of  Transverse  and  Compressive  Tests,  1905 .  70 

Beams  Made  with  Different  Brands  of  Cement,  Comparative  Density 

and  Strength .  73 

Permeability  Tests .  74 

Method  of  Making  Permeability  Tests .  74 

Apparatus  for  Testing  Permeability.  .  . .  76 

Recording  the  Data .  76 

Adhesion  of  Cement  Casing  to  Concrete  Block .  78 

Results  of  Permeability  Tests .  78 

Effect  of  Per  Cent,  of  Cement  upon  Permeability .  78 

Effect  of  Size  of  Stone  upon  Permeability .  78 

Decrease  of  Permeability  with  Age .  79 

Increase  of  Permeability  with  Pressure .  80 

Effect  of  Thickness  of  Concrete  upon  Permeability . .  80 

Rate  of  Flow  During  A  Four-Hour  Period .  80 

Comparative  Strength  of  Mortars  and  Permeability  of  Concretes 

with  Several  Available  Sands .  81 

Volumetric  Tests  of  Density  of  Neat  Cement  and  Mortar .  83 

Effect  of  Different  Percentages  of  Water  upon  Volume  and  Density.  83 

Tensile  Tests  of  Neat  Cement  Used  in  Concrete  Beams,  1905 .  84 

Mechanical  Analysis  of  Average  Jerome  Park  and  Cowe  Bay  Mate¬ 
rials  Used  in  Beam  Tests .  85 

Elasticity  Tests .  86 

Effect  of  Size  of  Stone  on  Modulus  of  Elasticity .  92 

Effect  of  Percentage  of  Cement  on  Modulus  of  Elasticity .  92 

Effect  of  Character  of  Material  on  Modulus  of  Elasticity .  92 


CITY  OF  NEW  YORK 


THE  AQUEDUCT  COMMISSIONERS 


Hon.  GEORGE  B.  McCLELLAN,  Mayor ; 
HERMAN  A,  METZ,  Comptroller ; 
JOHN  F.  COWAN; 

JOHN  P.  WINDOLPH; 
WILLIAM  H.  TEN  EYCK; 

JOHN  J.  RYAN. 


WALTER  H.  SEARS,  Chief  Engineer. 


Printed  in  Accordance  with  a  Resolution  of 
THE  AQUEDUCT  COMMISSIONERS 
March  16,  1906. 


Digitized  by  the  Internet  Archive 
in  2017  with  funding  from 

University  of  Illinois  Urbana-Champaign  Alternates 


https://archive.org/details/reportofresultexOOnewy 


170  Broadway,  New  York  City, 
Oct.  11,  1905. 

To  the  Aqueduct  Commissioners ,  New  York  City: 

Gentlemen  : 

In  accordance  with  your  resolution  and  acting  under  the  in¬ 
structions  of  your  Chief  Engineer,  I  herewith  present  a  report  on 
the  results  of  the  concrete  experiments  made  at  Jerome  Park  Reser¬ 
voir  during  the  past  two  years. 

The  object  of  the  tests  has  been  the  comparative  study  of  the 
laws  governing  the  mixtures  of  cement  and  aggregates  for  con¬ 
crete  with  a  view  to  determine  the  most  economical  mixtures  and 
the  mixtures  giving  the  greatest  strength  and  impermeability  with  a 
minimum  percentage  of  cement,  with  special  reference  to  the  ad¬ 
visability  and  propriety  of  using  materials  available  at  Jerome  Park 
Reservoir  in  that  work. 

Previous  tests  and  studies  of  the  writer  indicated  that  with  the 
same  percentage  of  cement,  but  different  arrangement  of  the  ag¬ 
gregates,  the  strongest  concrete  is  that  in  which  the  aggregate  is 
proportioned  so  as  to  give  a  concrete  of  the  greatest  density,  that 
is,  with  the  smallest  percentage  of  voids.  With  this  law  established, 
it  would  be  possible  to  compare  the  value  of  different  aggregates 
and  various  proportions  of  the  same  aggregates  by  volumetric  tests, 
the  best  mixture  in  general  giving  the  smallest  volume  of  concrete. 

The  tests  were  accordingly  arranged  with  the  view  to  fix  the 
limitations  of  this  theory,  to  ascertain  the  effect  of  different  ag¬ 
gregates  upon  the  density,  strength  and  permeability  of  concrete, 
and  particularly  to  determine  the  exact  sizes  of  aggregate  which, 
mixed  together  with  a  given  proportion  of  cement,  would  form  the 
best  concrete.  The  density  and  strength  of  concrete  made  up  of 
an  aggregate  of  ideal  mechanical  analysis  and  of  different  maximum 
size  was  compared  with  the  density  and  strength  of  concrete  made 
of  average  sand  and  stone  or  gravel  in  ordinary  nominal  mixtures. 


4 


The  relative  permeability  of  concrete  with  different  aggregates 
and  different  proportions  of  cement  was  also  studied. 

In  this  connection  it  became  necessary  to  study  many  related 
subjects,  such  as  the  physical  characteristics  of  different  cements, 
broken  stone,  broken  stone  screenings,  gravel  and  sand,  especially 
with  reference  to  specific  gravity,  weight,  voids,  density,  etc.  Each 
material  was  tested  by  itself  and  when  mixed  in  various  proportions 
with  others. 

The  methods  and  results  of  all  these  studies  are  given  in  detail 
in  the  accompanying  appendix  by  Mr.  Sanford  E.  Thompson,  Mem. 
Am.  Soc.  C.  E.,  who  had  direct  supervision  of  the  details  of  the 
tests  and  arrangement  of  their  records. 

The  practical  side  of  the  question  was  not  lost  sight  of;  in  fact, 
all  of  the  preliminary  studies  were  made  to  throw  light  on  the  best 
attainable  concrete  in  the  actual  construction  of  the  reservoir,  and 
from  the  results  of  these  studies  several  changes  were  made  from 
time  to  time  in  the  sizes,  proportions  and  methods  of  mixing  and 
placing,  which  it  is  believed  have  resulted  in  a  grade  of  concrete 
construction  at  the  reservoir  fully  in  accordance  with  the  best 
engineering  practice  of  the  day  and  of  a  higher  grade  than  was  at 
first  thought  practicable  under  the  contract. 

As  shown  by  the  tests,  an  ideal  mixture  of  Co  we  Bay  sand  and 
gravel  with  a  given  proportion  of  cement  gave  a  denser  concrete 
than  an  ideal  mixture  of  Jerome  Park  screenings  and  broken  stone 
with  the  same  proportion  of  cement,  but  on  the  other  hand,  there 
was  under  equal  conditions  a  stronger  adhesion  of  the  cement  to 
the  broken  stone  than  to  the  gravel.  As  the  proportion  of  cement 
specified  for  the  reservoir  construction  was  such  as  to  produce  im¬ 
permeability  in  either  case,  it  was  advised  that  screenings  and 
broken  stone  be  used  on  account  of  the  additional  adhesion. 

The  following  conclusions  have  been  drawn  from  the  tests. 
Many  of  these  introduce  laws  which  we  believe  have  not  hitherto 
been  recognized,  and  which  are  opposed  in  certain  cases  to  current 
ideas,  so  that  some  of  the  conclusions  are  of  a  tentative  character 
and  require  further  confirmation. 

1. — The  largest  size  stone  makes  the  strongest  concrete  under 
both  compression  and  transverse  loading,  i.  e.,  an  aggregate  whose 
maximum  size  stone  is  2i  in.  diameter  gives  stronger  concrete  than 


5 


an  aggregate  with  1  in.  maximum  size,  and  the  1-in.  stone  gives  a 
stronger  concrete  than  a  |-in.  stone.  A  concrete  whose  aggregate 
runs  to  1  in.  maximum  size  will  require  for  equal  strength  about  & 
more  cement,  and  with  aggregate  running  to  i  in.  maximum  size 
about  i  more  cement  than  concrete  with  aggregate  whose  maximum 
size  is  2\  in. 

2.  — The  largest  stone  makes  the  densest  concrete.  Concrete 
made  with  stone  having  a  maximum  diameter  of  2£  in.  is  notice¬ 
ably  denser  than  that  with  1-in.  stone,  and  this  is  denser  than  that 
with  i-in.  stone. 

3.  — Round  material  like  gravel  gives  under  similar  conditions 
a  denser  concrete  than  broken  stone. 

4.  — Sand  produces  a  denser  concrete  than  screenings  when  used 
with  the  same  proportions  of  stone  and  cement. 

5.  — Cement,  sand  and  gravel  concrete  is  stronger  than  concrete 
•of  cement,  screenings  and  broken  stone,  probably  because  of  this 
greater  density.  Concrete  of  cement,  sand  and  broken  stone,  how¬ 
ever,  is  found  to  be  stronger  than  concrete  of  cement,  sand  and 
gravel,  although  the  latter  mix  is  denser,  thus  indicating  a  stronger 
adhesion  of  cement  to  broken  stone  than  to  gravel. 

6.  — Aggregates  whose  mechanical  analysis  (including  the  cement), 
has  been  formed  so  as  to  give,  when  water  is  added,  an  artificial 
mixture  of  greatest  density  produce  concrete  of  higher  strength 
than  mixtures  of  cement  and  natural  materials  in  similar  propor¬ 
tions.  The  average  improvement  in  strength  by  artificial  grading 
under  the  conditions  of  the  tests  was  about  14  per  cent.  Comparing 
the  tests  of  strength  of  concrete  having  different  percentages  of  ce¬ 
ment,  it  is  found  that  for  similar  strength  the  best  artificially 
graded  aggregate  would  require  about  12%  less  cement  than  like 
mixtures  of  natural  materials.  Artificial  grading  to  obtain  strength 
is  evidently  economical  only  up  to  the  point  where  its  additional  cost 
is  equal  to  the  cost  of  cement  saved  by  the  process. 

7.  — The  ideal  mechanical  analysis  curve,  i.  e.,  the  best  curve, 
is  slightly  different  for  different  materials.  Cowe  Bay  sand  and 
gravel,  for  example,  pack  closer  than  Jerome  Park  stone  and  screen¬ 
ings,  and  therefore  require  less  of  the  size  of  grain  which  we  desig¬ 
nate  as  sand. 

8.  — The  tests  indicate  that  the  best  mixture  of  cement  and  ag- 


e 


gregate  has  a  mechanical  analysis  curve  resembling  a  parabola, 
which  is  a  combination  of  a  curve  approaching  an  ellipse  for  the 
sand  portion  and  a  tangent  straight  line  for  the  stone  portion.  The 
ellipse  runs  to  a  diameter  to  the  diameter  of  the  maximum  size 
stone,  and  the  stone  from  this  point  is  uniformly  graded. 

9.  — The  strength  and  density  of  concrete  appears  to  be  but 
slightly,  if  at  all,  affected  by  decreasing  the  quantity  of  the  medium 
size  stone  of  the  aggregate  and  increasing  the  quantity  of  the 
coarsest  stone.  An  excess  of  stone  of  medium  size,  on  the  other 
hand,  appreciably  decreases  the  density  and  strength  of  the  con¬ 
crete. 

10.  — The  density  of  concrete  is  affected  by  the  variation  in  di¬ 
ameter  of  the  particles  of  sand  more  than  by  variation  in  the  diame¬ 
ters  of  the  stone  particles,  provided  the  maximum  diameter  of  the 
stone  remains  the  same  and  there  is  not  an  excess  of  medium-size 
stone. 

11.  — An  excess  of  fine  or  of  medium  sand  decreases  the  density 
and  also  the  strength  of  the  concrete,  while,  on  the  other  hand,  a 
deficiency  of  fine  grains  of  sand  in  a  lean  concerte  may  result  in  un¬ 
filled  voids. 

12.  — The  form  of  the  best  analysis  curve  for  any  given  material 
is  nearly  the  same  for  all  sizes  of  stone,  that  is,  the  curve  for  l*in., 
1-in.,  and  21 -in.  maximum  stone  may  be  described  by  an  equation 
with  the  maximum  diameter  as  the  only  variable.  In  other  words, 
suppose  a  diagram  in  which  the  left  ordinate  is  zero,  and  the  ex¬ 
treme  right  ordinate  corresponds  to  21-in.  stone,  with  the  best  curve 
for  this  stone  drawn  upon  it.  If,  now,  on  this  diagram  the  vertical 
scale  remains  the  same,  but  the  horizontal  scale  is  increased  two 
and  a  quarter  times,  so  that  the  diameter  of  1-in.  stone  corresponds 
to  the  extreme  right-hand  ordinate,  the  best  curve  for  the  1-in.  stone 
will  be  very  nearly  the  one  already  drawn  for  the  21-in.  stone.  The 
chief  difference  between  the  two  appears  to  be  that  the  larger  size 
stone  requires  a  slightly  higher  curve  in  the  fine  sand  portion.  If 
the  two  curves  are  drawn  to  the  same  scale,  the  21-in.  curve  is  of 
course  lengthened  out  so  that  much  less  fine  material  is  actually 
required  than  for  the  1-in.  curve. 

13.  — It  follows  from  this  last  conclusion  that  from  a  scientific 
standpoint  the  term  sand  is  a  relative  one.  With  21-in.  stone,  the 


7 


best  sand  would  range  in  size  from  0  to  0.22  in.  diameter,  while 
the  best  sand  for  ^-in.  stone  would  range  in  size  from  0  to  0.05  in. 
diameter. 

14.  — In  ordinary  proportioning  with  two  given  kinds  of  aggre¬ 
gate  and  a  given  percentage  of  cement,  the  densest  and  strongest 
mixture  is  attained  when  the  volume  of  the  mixture  of  sand,  ce¬ 
ment  and  water  is  so  small  as  to  just  fill  the  voids  in  the  stone.  In 
ether  words,  in  practical  construction  use  as  small  a  proportion  of 
sand  and  as  large  a  proportion  of  stone  as  is  possible  without  pro¬ 
ducing  visible  voids  in  the  concrete. 

15.  — The  substitution  of  cement  for  fine  sand  of  the  same  size 
grains  does  not  affect  the  density  of  the  mixture,  but  increases  the 
strength,  although  in  a  slightly  smaller  ratio  than  the  increase  in 
the  percentage  of  cement. 

16.  — Correct  proportioning  of  concrete  consists  in  finding  with 
any  percentage  of  cement  a  concrete  mixture  of  maximum  density, 
and  increasing  or  decreasing  the  cement  by  substituting  it  for  sand 
having  the  same  size  grains  or  vice  versa.  This  very  important  law 
requires  further  tests  for  complete  demonstration,  since  certain  of 
the  results  are  inconclusive. 

17. — Permeability  or  rate  of  flow  through  concrete  is  less  as 
the  per  cent,  of  cement  is  increased,  and  in  very  much  larger  in¬ 
verse  ratio. 

18.  — Rate  of  flow  is  less  as  the  maximum  size  of  the  stone  is 
greater.  Concrete  with  maximum  size  stone  of  2^-in.  diameter  is, 
in  general,  less  permeable  than  one  with  1-in.  diameter  maximum 
stone,  and  this  is  less  permeable  than  one  with  i-in.  stone. 

19.  — Concrete  of  cement,  sand  and  gravel  is  less  permeable— 
that  is,  the  rate  of  flow  is  less— than  concrete  of  cement,  screenings 
and  broken  stone.  The  difference,  however,  is  a  relative  one,  and 
indicates  that  for  equal  permeability  a  slightly  less  amount  of  ce¬ 
ment  is  required  •  with  rounded  aggregates  like  gravel  than  with 
sharp  aggregates  like  broken  stone. 

20.  — Concrete  of  mixed  broken  stone  and  sand  is  more  permeable 
than  concrete  of  gravel  and  sand,  and  less  permeable  than  con¬ 
crete  of  broken  stone  and  screenings,  which  indicates  that  for 
water-tightness  less  cement  is  required  with  rounded  sand  and 
gravel  than  with  broken  stone  and  screenings. 


8 


21.  — The  rate  of  flow  decreases  materially  with  age. 

22.  — Rate  of  flow  increases  nearly  uniformly  with  the  increase 
in  pressure. 

23.  — Rate  of  flow  increases  as  the  thickness  of  the  concrete  de¬ 
creases,  but  in  a  much  larger  inverse  ratio. 

The  use  of  concrete  in  water  works  construction  is  yet  in  its 
infancy,  and  there  are  yet  many  unsolved  questions  relating  to  its 
properties  which  are  not  touched  upon  in  this  report,  or  need  fur¬ 
ther  investigation  for  confirming  the  tentative  conclusions  now  ar¬ 
rived  at,  and  I  would  recommend  that  these  tests  be  continued 
along  the  following  general  lines: 

A.  Further  tests  to  confirm  the  conclusions  on  relation  of 
density  to  strength,  in  order  to  more  fully  adapt  the  laws  to  prac¬ 
tical  proportioning  in  the  field. 

B.  Further  permeability  tests  to  establish  laws  for  proportion¬ 
ing  water-tight  concrete  and  fixing  required  thickness  for  different 
heads. 

C.  Tests  to  determine  relative  economy  of  plain  vs.  reinforced 
structures  in  hydraulic  designs. 

More  specifically,  tests  in  the  directions  just  mentioned  may  be 
enumerated : 

1.  — Specific  tests  in  connection  with  the  design  of  structures 
about  to  be  built. 

2.  — Comparison  of  water-tightness  of  different  thicknesses  of 
concrete  and  mortar  to  determine  proper  thicknesses  of  concrete  of 
different  proportions  for  given  heads. 

3.  — Determination  of  relative  permeability  of  mortar  and  of  ^ 
concrete  made  with  this  same  mortar. 

4.  — Determination  of  relative  permeability  of  mortars  of  coarse 
and  fine  sand  and  various  mixtures  of  sand. 

5.  — Further  tests  upon  relative  permeability  of  concrete  with 
different  sizes  of  coarse  aggregate. 

6.  — Determination  of  effect  upon  impermeability  of  adding  and 
substituting  Puzzolan  cement. 

Y. — Determination  of  effect  upon  permeability  of  adding  and 
substituting  hydrated  lime. 

8. — Study  of  effect  of  troweling  and  other  treatment  of  the  sur¬ 
face  upon  permeability. 


9.  — Continuation  of  tests  relating  to  density  vs.  strength  of 
concrete  to  confirm  the  laws  established  tentatively. 

10.  — Extension  of  the  series  of  tests  just  completed  with  richer 
and  leaner  mixtures  to  formulate  a  law  and  evolve  formulas  by 
which  the  strength  of  a  specimen  made  with  a  certain  brand  of 
cement  may  be  calculated  from  its  density. 

11- — Comparison  of  effect  of  different  classes  of  coarse  stone, 
such  as  limestone,  sandstone,  and  trap,  upon  the  strength  and  per¬ 
meability  of  concrete. 

12.  — Determination  of  effect  of  the  surface  of  the  stones  upon 
the  strength  of  the' concrete. 

13.  — Tests  to  determine  under  what  conditions  the  ultimate 
strength  of  a  concrete  is  dependent  solely  upon  the  character  of  the 
coarse  aggregate.  When  such  is  the  case,  a  lean  mixture  on  a  long 
time  test  will  catch  up  to  a  rich  mixture,  and  a  mixture  in  which 
a  portion  of  the  cement  is  replaced  by  an  inert  fine  material  will 
be  equivalent  in  strength  and  water-tightness  to  a  richer  mixture 
for  structures  which  will  not  be  used  immediately. 

14.  — Evolution  of  formulas  by  which,  having  given  the  mechan¬ 
ical  analysis  of  an  aggregate,  and  its  percentage  of  a  certain  brand 
of  cement,  the  density,  strength  and  water-tightness  may  be  ap¬ 
proximately  calculated. 

15.  — Study  of  effect  of  the  fineness  of  the  cement  upon  the 
density  and  strength  of  a  mortar.  The  necessity  for  such  study 
is  shown  by  the  fact  that  while  an  increase  in  the  fineness  of  a  ce¬ 
ment  appears  to  increase  its  cementitious  value,  there  may  be  an 
economical  limit  of  fineness  because  the  very  fine  grains  tend  to 
be  chemically  acted  upon  by  an  excess  of  water  so  as  to  form 
laitance,  and  also  tend  to  increase  the  bulk  of  the  paste.  It  is  thus 
impossible  to  reduce  the  density  of  a  mortar  below  a  certain  point, 
and  this  limits  the  strength  which  the  mortar  can  attain. 

16.  — Tests  of  the  resistance  to  erosion  of  concretes  made  up  of 
various  aggregates,  sand  and  cement. 

In  conclusion  I  desire  to  express  to  my  assistants  in  this  work 
my  hearty  appreciation  of  their  interest  and  zeal,  without  which  co¬ 
operation  the  results  accomplished  with  the  time  and  funds  available 
would  have  been  impossible.  Especial  thanks  are  due  to  Mr. 


10 


Thomas  H.  Wiggin,  for  his  valued  advice  and  assistance  in  start¬ 
ing  the  experiments;  to  Mr.  William  Hauck,  for  his  careful  atten¬ 
tion  to  the  large  amount  of  calculations  involved  in  the  tables  of 
this  report,  and  to  Messrs.  James  L.  Davis,  Charles  M.  Mont¬ 
gomery,  and  William  E.  King,  for  their  faithful  labors  in  con¬ 
nection  with  the  tests. 

Kespectfully  submitted, 

Wm.  B.  Euller, 

Expert 


APPENDIX. 


DETAILS  OF  METHODS  AND  RESULTS  OF  CON¬ 
CRETE  TESTS  FOR  THE  AQUEDUCT 
COMMISSIONERS, 

MADE  AT  JEROME  PARK  RESERVOIR,  NEW  YORK  CITY, 

1904-5. 

By  Sanford  E.  Thompson. 


Description  of  Tests. 

Experiments  made  by  Mr.  Puller  at  Little  Falls,  N.  J.,  in  1901, 
upon  the  density  and  transverse  strength  of  concrete  beams  mixed 
in  various  proportions,  by  weight,  ranging  in  proportions  from  1 :  0 
to  1 :  6 : 10,  indicated  that  the  strength  of  concrete  varies  with 
the  percentage  of  cement  contained  in  a  unit  volume  of  the  set  con¬ 
crete,  and  also  with  the  density  of  the  specimen.  With  the  same  per¬ 
centage  of  cement  in  a  given  volume  of  concrete,  the  densest  mix¬ 
ture,  irrespective  of  the  relative  proportions  of  the  sand  and  stone, 
was  in  general  the  strongest. 

The  Little  Falls  tests  further  indicated  that  for  the  materials 
used  there  was  a  certain  mixture  of  sizes  of  grains  of  the  aggre¬ 
gate  which,  with  a  given  percentage,  by  weight,  of  cement  to  the 
total  aggregate,  gave  the  highest  breaking  strength.  In  practice, 
also,  it  was  found  that  the  concrete  made  with  this  mixture  worked 
most  smoothly  in  placing.  The  mixture  of  sizes  of  particles  of 
aggregate  which  appeared  to  give  the  best  results  gave  for  its  me¬ 
chanical  analysis  a  curve  approaching  a  parabola,  with  its  beginning 
at  zero  co-ordinates,  and  passing  through  the  intersection  of  the 
curve  of  the  coarsest  stone  with  the  100%  line,  that  is,  passing 
through  the  upper  end  of  the  coarsest  stone  curve. 

Graded  stone  of  the  same  maximum  diameter  and  character 
was  used  in  all  the  Little  Falls  experiments,  and  the  laws  men- 


12 


tioned  were  discovered  by  a  comparison  of  the  final  results  from 
the  tests  rather  than  by  logical  investigation.  Therefore,  before 
the  laws  could  be  fully  established,  further  experiments  were  essen¬ 
tial  with  other  materials  and  mixtures,  together  with  a  careful 
study  into  the  limitations  of  the  laws. 

The  purpose  of  the  experiments  at  Jerome  Park  Reservoir  was 
not  only  to  obtain  results  which  might  prove  of  practical  value  in 
the  construction  of  the  reservoir,  but  to  go  further  and  make  a 
more  general  study  with  the  object  of  assisting  in  the  design  of  other 
structures  to  be  subsequently  built  for  the  water  supply  of  New 
York.  The  study,  therefore,  was  chiefly  of  the  laws  of  proportion¬ 
ing  plain  concrete,  to  determine  the  mixtures  which  would  give 
maximum  strength  and  water-tightness  at  the  least  cost. 

The  experiments  were  begun  with  a  series  of  tests  of  the  density 
of  different  mixtures  of  aggregates  and  cement  to  study  the  laws  of 
proportioning  for  maximum  density  with  different  materials,  and 
these  density  experiments  were  followed  with  the  manufacture  of 
concrete  beams  6  in.  by  6  in.  by  72  in.  for  comparing  the  laws  of 
strength  with  the  laws  of  density,  and  determining  the  relation  be¬ 
tween  these  two  causes.  As  the  compressive  strength  of  concrete  is  a 
truer  measure  of  its  quality  than  the  transverse  strength,  which 
in  the  case  of  concrete  is  really  one  form  of  tension  test,  two  pieces 
of  each  beam  after  being  broken  in  the  beam  machine  were  capped 
with  neat  cement  so  as  to  form  prisms  about  6  in.  square  and  18 
in.  long,  and  these  were  tested  for  compressive  strength  and  a  num¬ 
ber  of  them  were  also  tested  for  the  compressive  modulus  of  elas¬ 
ticity.  A  selected  number  of  pieces  of  the  broken  beams  were  also 
tested  for  permeability. 

Other  secondary  experiments  upon  the  density  of  mortars  and 
the  quantity  of  water  required  for  different  sizes  of  sand  were  be¬ 
gun,  and  although  not  extended  far  enough  to  reach  definite  con¬ 
clusions,  the  results  are  of  interest  as  indicating  the  possibilities 
of  another  important  line  of  investigation.  It  was  intended  to  use 
these  results  further  as  preliminary  to  a  series  of  permeability  tests 
of  mortars  composed  of  cement  and  sand  of  different  size  grains, 
and  containing  admixtures  of  Puzzolan  cement  and  of  hydrated 
lime. 

One  of  the  valuable  results  of  the  present  series  of  concrete  tests 


13 


was  the  discovery  of  a  method  for  testing  the  permeability  of  speci¬ 
mens  of  different  composition  and  thickness  by  simply  coating  the 
sides  with  neat  cement  and  forming  a  dome  over  the  top,  which  was 
readily  connected  with  a  tank  of  water  under  various  pressures. 
The  methods  of  making  all  of  the  tests  and  the  apparatus  employed 
are  briefly  described  in  subsequent  paragraphs. 


Mechanical  Analysis.* 


Mechanical  analysis  consists  in  separating  the  particles  or  grains 
of  a  sample  of  any  material — such  as  broken  stone,  gravel,  sand  or 
cement — into  the  various  sizes  of  which  it  is  composed,  so  that 
the  material  may  be  represented  by  a  curve  (see  Fig.  2,  p.  15)  each 
of  whose  ordinates  is  the  percentage  of  the  weight  of  the  total 
sample  which  passes  a  sieve  having  holes  of  a  diameter  represented 
by  the  distance  of  this  ordinate  from  the  origin  in  the  diagram. 

The  objects  of  mechanical  analysis  curves  as  applied  to  con¬ 
crete  aggregates  are  (1)  to  show  graphically  the  sizes  and  relative 
sizes  of  the  particles;  (2)  to  indicate  what  sized  particles  are 
needed  to  make  the  aggregate  more  nearly  perfect  and  so  enable 
the  engineer  to  improve  it  by  the  addition  or  substitution  of  an¬ 
other  material;  and  (3)  to  afford  means  for  determining  best  pro¬ 
portions  of  different  aggregates. 

To  determine  the  relative  sizes  of  the  particles  or  grains  of 
which  a  given  sample  of  stone  or  sand  is  composed,  the  different 
sizes  are  separated  from  each  other  by  screening  the  material 
through  successive  sieves  of  increasing  fineness.  After  sieving, 
the  residue  on  each  sieve  is  carefully  weighed,  and  beginning  with 
that  which  has  passed  the  finest  sieve,  the  weights  are  successively 
added,  so  that  each  sum  will  represent  the  total  weight  of  the 
particles  which  have  passed  through  a  certain  sieve.  The  sums 
thus  obtained  are  expressed  as  percentages  of  the  total  weight  of 
the  sample  and  plotted  upon  a  diagram  with  diameters  of  the 
particles  as  abscissas  and  percentages  as  ordinates. 

The  method  of  plotting  and  the  uses  of  the  curves  thus  ob¬ 
tained  are  more  fully  described  in  the  pages  which  follow. 

Sieves  and  Other  Apparatus. — Fig.  1  illustrates  a  convenient 
outfit  for  such  a  mechanical  analysis  as  above  described,  consisting 
of  a  set  of  sieves,  an  apparatus  for  shaking  the  sieves,  and  scales 
for  weighing.!  A  standard  size  of  sieve  is  8  in.  in  diameter  and 


..  paragraphs  and  diagrams  under  this  heading  are  quoted  by  permission  from 

the  chapter  by  Mr.  Fuller  on  Proportioning  Concrete,  in  Taylor  and  Thompson’s  “Con¬ 
crete,  Plain  and  Reinforced,”  1905. 


t  This  apparatus  is  used  in  the  laboratory  at  Jerome  Park. 


14 


2i  in.  high.  Sieves  with  openings  exceeding  0.10  in.  are  preferably 
made  of  spun  hard  brass  with  circular  openings  drilled  to  the 
exact  dimensions  required.  Sieves  with  openings  of  0.10  in.  and 
less  are  preferably  of  woven  brass  wire  set  into  a  hard  brass  frame. 
Woven  brass  sieves  are  made  for  many  purposes,  and  are  sold  by 
numbers  which  approximately  coincide  with  the  number  of  meshes 
to  the  linear  inch.  As  the  actual  diameter  of  the  hole  varies  with 
the  gage  of  wire  used  by  different  manufacturers,  every  set  of  sieves 
must  be  separately  calibrated. 

An  approximate  idea  of  the  diameters  of  holes  which  may  be 
expected  in  commercial  sizes  of  sieves  is  presented  in  the  follow¬ 
ing  table,  which  is  sufficiently  exact  to  serve  as  a  guide  to  the  pur¬ 
chase  of  the  sieves: 


Commercial 

No.  of  sieve. 

Diameter 
of  hole 
in  inches. 

Commercial 

No.  of  sieve. 

Diameter 
of  hole 
in  inches. 

10 

0.073 

60 

0.009 

15 

0.047 

74 

0.0078 

16 

0.042 

100 

0.0045 

18 

0.037 

140 

0.003625 

20 

0.034 

150 

0.00325 

30 

0.022 

170 

0.0031 

35 

0.017 

180 

0.00306 

40 

0.015 

190 

0.0028 

50 

0.011 

200 

0.00275 

For  separating  particles  smaller  than  those  passing  through  a 
No.  200  sieve,  recourse  must  be  had  to  processes  of  elutrition  which 
have  been  developed  to  great  precision  by  soil  analysis  chemists. 

In  selecting  the  right  series  of  sieves  to  purchase,  first  decide 
on  the  limiting  diameters,  say,  from  3.00  in.  to  No.  200  =  0.00275 
in.  Then  decide  on  the  total  number  of  sieves,  say,  twenty.  Look 
up  the  logarithm  of  3.00  and  of  0.00275  and  by  proportion  find 
eighteen  other  logarithms  between  these  having  equal  difference 
between  each.  Look  for  the  number  corresponding  and  take  the 
nearest  commercial  sieve  giving  this  diameter.  The  diameters  of 
holes  exceeding  0.10  in.  can  be  made  as  required.  A  convenient 
set  of  twenty  sieves — ten  for  stone,  which  give  the  diameter  of  the 
holes  in  inches,  and  ten  for  sand,  giving  the  commercial  number 
— is  as  follows:* 

*  These  sizes  nearly,  but  not  quite,  correspond  to  those  adopted  at  Jerome  Park 
laboratory,  which  are  tabulated  on  page  22. 


I2E  jvrnm 

•"LLOllD- 

■f  "'rwT*' f  I : 

a  jr  » 

tv 


if. 

i  •  ,  i  1  i  -*W  \b#  / 

i  si 


W'a 


$=s 


Fig.  1.— Outfit  for  Mechanical  Analysis  of  Aggregates. 


PEftCENf,  By  WElGHt,  SMALLER  Than  GIVEN  BlAMETEft 


15 


Stone  sieves, 
inches. 

Sand  sieves, 
Commercial  No. 

Stone  sieves, 
inches. 

Sand  sieves, 
Commercial  No. 

3  00 

10 

0.45 

60 

2.25 

15 

0.30 

74 

1.50 

20 

0.20 

100 

1.00 

30 

0.15 

150 

0.67 

40 

0.10 

200 

After  the  sieves  are  obtained  it  is  necessary  that  they  should  be 
very  carefully  calibrated  to  ascertain  the  average  diameter  of  the 
mesh.  This  should  be  done  by  averaging  the  diameters  of  the  open¬ 
ings  measured  in  two  positions  at  right  angles  to  each  other,  as  the 
meshes  of  commercial  sieving  are  not  exactly  square.  Sieves  havi  .ig 
meshes  exceeding  0.10  inch  are  most  conveniently  calibrated  by 
ordinary  outside  calipers;  those  having  meshes  of  less  diameter,  by 
a  micrometer  microscope. 

Plotting  Analysis  Curves. — Tor  those  who  are  unfamiliar  with 
mechanical  analysis  a  detailed  explanation  of  the  method  of  locating 
the  curve  is  here  given.  The  method  can  best  be  understood  by 
referring  to  the  diagrams  of  typical  materials  which  are  also  of 
practical  interest  as  illustrating  the  curves  which  may  be  expected 
in  special  cases. 

Tig.  2  represents  a  typical  mechanical  analysis  of  crusher- 
run  micaceous  quartz  stone  which  has  been  run  through  a  \ -in. 
revolving  screen  so  as  to  separate  particles  finer  than  \  in.,  that  is 
the  dust,  for  use  with  sand. 


Fig.  2.— Typical  Mechanical  Analysis  of  Micaceous  Quartz  Crusher  Run  Stone. 


For  a  sample  of  stone,  which  may  be  taken  by  the  method  of 
quartering,  1  000  grams  is  a  convenient  quantity  for  8-in.  diameter 
sieves  2J  in.  in  depth,  and  also  permits  of  easy  reduction  from 
weights  to  percentages.  To  obtain  the  analysis  shown  in  Fig.  2  the 
sample  of  stone  is  placed  in  the  upper  (coarsest)  sieve  of  the  nest 
of  stone  sieves  given  on  page  15  and  after  1  000  shakes  the  nest  is 
taken  apart,  and  the  quantity  caught  on  each  sieve  is  weighed. .  The 
results  obtained  in  the  particular  case  under  consideration  are  illus¬ 
trated  in  the  following  table,  which  shows  the  method  of  finding 
the  percentages: 


Results  of  Screening  Samples  of  Stone  of  Fig .  2. 


Size  sieve,  inches. 

Retained  in  each 
sieve*,  grams. 

Amount  finer  than 
each  sieve,  grams. 

Percent,  finer  than 
each  sieve. 

0.10 

8 

0 

0.15 

11 

8 

1 

0.20 

8 

19 

2 

0.30 

72 

27 

3 

0.45 

123 

99 

10 

0.67 

235 

222 

22 

1.00 

344 

457 

46 

1.50 

199 

801 

80 

Total . 

100 

. 

- I - I - 

*  In  practise  this  column  is  not  required,  the  weights  in  the  next 
tained  directly  by  placing  each  successive  residue  on  the  scale  pan  with  that  already 
weighed. 


The  various  percentages  are  plotted  on  the  diagram  and  the 
curve  drawn  through  the  points.  The  vertical  distance  from  tne 
bottom  of  the  diagram  to  the  curve,  that  is,  the  ordinate  at  any 
point,  represents  the  percentage  of  the  material  which  passed 
through  a  single  sieve  having  holes  of  the  diameter  represented  hy 
this  particular  ordinate.  Since  the  percentage  of  material  passing 
any  sieve  is  always  the  complement  of  the  percentage  of  grains 
coarser  than  that  sieve,  the  vertical  distances  from  the  top  of  the 
diagram  down  to  the  curve  represents  the  percentages  which  would 
be  retained  upon  each  sieve  if  employed  alone.  For  example,  tak¬ 
ing*  1.25,  62%,  the  distance  from  the  bottom  of  the  diagram,  repre¬ 
sents  the  percentage  of  material  finer  than  li  in.  diameter,  and  38%, 
the  distance  down  from  the  top  of  diagram,  represents  the  per¬ 
centage  coarser  than  li  in. 


Preparation  of  Materials. 

Cement. — Portland  cement  from  the  regular  shipments  to  the 
reservoir  was  used  in  all  except  a  few  comparative  tests  of  different 


IT 


brands.  This  cement  had  been  tested  in  the  regular  fashion  for 
reservoir  work,  and,  in  addition,  every  bag  which  was  used  in  the 
later  experiments  was  subjected  to  the  purity  test.  It  was  found 
that  the  cement  used  in  the  1904  beams  which  did  not  set  up  satis¬ 
factorily,  failed  to  pass  this  test,  while  all  the  cement  passing  this 
test  appeared  satisfactory  from  a  chemical  standpoint. 

Purity  Test. — The  purity  test  is  as  follows: 

Provide  a  glass-stoppered  bottle  of  muriatic  acid,  two  shallow 
white  bowls  or  two  i-inch  by  6-inch  test  tubes,  a  glass  rod,  and  a 
pair  of  rubber  gloves.  Put  in  a  bowl  or  a  tube  as  much  cement  as 
can  be  taken  on  a  nickel  5-cent  piece;  moisten  it  with  half  a  tea¬ 
spoonful  of  water;  cover  with  clear  muriatic  acid  poured  slowly 
upon  the  cement  while  stirring  it  with  the  glass  rod.  Pure  Port¬ 
land  cement  will  effervesce  slightly,  give  off  some  pungent  gas,  and 
gradually  form  a  bright  yellow  jelly  without  any  sediment.  Pow¬ 
dered  limestone  or  powdered  cement-rock  mixed  with  the  pure  ce¬ 
ment  will  cause  a  violent  effervescence,  the  acid  boiling  and  giving 
off  strong  fumes  until  all  the  carbonate  of  lime  has  been  consumed, 
when  the  bright  yellow  jelly  will  form.  Powdered  sand  or  quartz 
or  silica  mixed  with  cement  will  produce  no  other  effect  than  to  re¬ 
main  undissolved  as  a  sediment  at  the  bottom  of  the  yellow  jelly. 
Eeject  cement  which  has  either  of  these  adulterants.* 

Aggregate. — Two  classes  of  materials  were  used  for  the  aggre¬ 
gate;  broken  stone  and  screenings  from  the  crushers  at  the  reservoir, 
and  Cowe  Bay  gravel  and  sand  dredged  from  the  river. 

The  stone  as  it  comes  from  the  crushers  at  Jerome  Park  is  run 
through  revolving  screens  to  remove  the  stones  greater  than  2 -in. 
diameter,  which  are  not  permitted  in  the  reservoir  lining,  and  to 
separate  the  screenings,  which  are  measured  separately  from  the 
broken  stone  in  proportioning  the  concrete. 

The  stone  and  screenings  were  brought  to  the  laboratory,  and 
the  screenings  dried  in  large  pans  on  the  stove.  To  hasten  the  dry¬ 
ing,  they  were  continually  stirred,  and  when  dry  fine  dust  freely 
arose  from  them,  tests  indicated  that  they  contained  no  appreciable 
moisture.  Tests  made  of  the  material  which  had  been  stored  in  the 
laboratory  for  some  time  during  the  winter  showed  that  it  did  not 
collect  enough  moisture  to  affect  the  weights  used  in  making  the 
tests. 

The  1904  beams  were  made  with  material  as  it  came  from  the 


*  Judson’s  City  Roads  and  Pavements,  1902. 


18 


crusher  screens,  this  series  being  for  approximate  comparison  of 
the  strength  of  different  proportions,  while  the  density  experiments 
were  in  progress.  The  density  tests  were  a  necessary  preliminary 
to  the  more  scientific  mixtures  made  in  1905. 

For  the  density  tests  and  the  specimens  made  in  1905,  the  stone 
and  screenings  were  separated  in  the  laboratory  by  twenty-one 
sieves  ranging  in  size  from  3-in.  openings  to  No.  200  mesh  the 
latter  corresponding  to  an  opening  of  .0027  in.  By  employing  dif¬ 
ferent  mixtures  of  the  sizes  separated  by  these  sieves,  it  was  pos¬ 
sible  to  obtain  an  infinite  variety  of  proportions. 

Character  of  Jerome  Parh  Rock. — The  rock  at  Jerome  Park  is 
technically  a  mica  schist,  although  the  mica  is  in  such  a  state  that 
it  does  not  form  in  concrete  or  mortar  planes  which  seriously  affect 
the  strength.  This  has  been  investigated,  and  discussed  in  a  pre¬ 
vious  report.  The  variation  in  the  quality  of  the  rock  at  different 
parts  of  the  reservoir  gave  some  trouble  in  the  laboratory  and  led 
to  less  accuracy  in  the  results  of  the  density  experiments,  and  in 
forming  the  proportions  of  the  mixtures,  than  if  the  specific  gravity 
had  been  uniform.  The  most  noticeable  difference  in  different 
ledges  was  in  the  predominance  of  quartz,  some  of  the  lots  being 
lighter  in  color  than  the  others.  Since  the  specific  gravity  of  the 
minerals  in  the  native  rock  ranged  from  2.6  to  3.2,  the  specific 
gravity  of  different  lots  of  screenings  varied  appreciably,  and  the 
specific  gravity  of  different  diameters  of  the  same  rock  also  varied 
because  some  of  the  minerals  of  which  the  rock  was  composed 
crushed  more  readily  than  others,  and  therefore  certain  sizes  con¬ 
tained  predominating  minerals  which  determined  their  specific 
gravities.  Specific  gravities  of  different  sizes  are  given  in  a  subse¬ 
quent  portion  of  this  report. 

Composition  of  Rock.— The  following  report  was  made  upon  the 
mica  in  the  screenings  by  Charles  P.  Berkey: 

Report  of  Tests  Made  for  Quantity  of  Mica  in  Two  Samples  of 

Crushed  Bock. 

No.  7 Jj-. — (Screenings  at  74  mesh),  and 

General  Mixture—  (Whole  rock  crushed  to  less  than  40). 

Tests  were  made  first  by  Heavy  Solution  (Thoulet’s  Solution), 
and  3  separations  made  in  each  case,  obtaining: 


19 


1st.  The  white  minerals  (lower  specific  gravity  constituents). 

2d.  The  lighter  weight  portion  of  the  dark  constituents,  that  is,  the 
most  flaky  micas  and  less  basic  ones,  or,  otherwise,  the  por¬ 
tion  that  floats  in  the  densest  solution. 

3d.  The  heaviest  minerals,  that  is,  all  that  sink  to  the  bottom  in  the 
densest  solution,  or  otherwise,  mostly  the  perfectly  fresh 
solid  micas,  and  a  little  magnetite,  a  little  zircon,  and  some 
hornblende. 

No.  74  with  this  method  gives  out  of  sample  of  5  g. 

1st.  White  minerals  . 2.977  g.  =  59.54% 

2d.  Middlings  . 982  g.  =  19.64% 

3d.  Heaviest  part  . 1.041  g.  =  20.82% 

Of  No.  1 — there  is  no  mica. 

Of  No.  2 — all  of  it  is  mica  =  .982  g. 

Of  No.  3 — 83%  is  mica  .  .  =  .864  g. 

In  No.  3  the  chief  impurity  is  hornblende. 

General  Sample — with  this  method  gives  in  5  g. 

1st.  White  constituents  . 2.848  g.  =  56.96% 

2d.  Middlings  . 913  g. 

3d.  Heaviest  constituents  =  1.239  g. 

In  these  No.  1  has  no  mica. 

No.  2  has  90%  mica . =  .821  g. 

No.  3  has  90%  mica . =  1.115  g. 

Total  mica  . =  1.846  g.  =  36.92% 

The  chief  impurity  in  No.  2  is  fine  grains  of  (No.  1). 

The  chief  impurity  in  No.  3  is  hornblende. 

Check  tests  were  tried  for  mechanical  separation  by  sliding  over 
an  incline  and  agitating  the  plate.  The  results  are  not  satisfactory 
in  every  case. 

For  No.  74 — 

The  separation  is  fairly  good. 

The  flaky  portion — mica  =  35%. 

The  general  sample — 

This  method  did  not  succeed. 

Too  much  fine  material,  i.  e.,  less  than  74  mesh. 

It  will  neither  roll  nor  slide — making  the  residue  much 
too  high  in  value. 

Conclusions  : 

1st.  About  74  mesh  is  the  best  size  to  work  with.  If  all  grains 
were  about  this  size  a  fairly  good  separation  could  be 
obtained. 


20 


2d.  In  the  average  crushed  sample,  unless  controlled  carefully 
to  avoid  over-fine  grains,  a  mechanical  separation  is  a 
failure. 

3d.  Thoulet’s  heavy  solution  will  separate  the  light  from  the 
dark  minerals  with  great  precision. 

(K  I  -j-  Hgl2,  proportion  1 : 2.24,  dissolved  in  distilled 
water  and  used  as  a  settling  hath.) 

4th.  About  90%  of  the  dark  constituents  of  the  rock  prove  to  be 
mica.  The  grains  are  prominently  flaky,  brown,  yellow, 
black  color,  with  very  perfect  clevage. 

5th.  The  average  amount  of  mica  seems  certainly  to  exceed  35% 
according  to  these  samples. 

(Signed)  Charles  P.  Berkey. 

New  York  City,  Apr.  27,  1904. 

Uselessness  of  Determination  of  Voids  in  Sand. — The  percen¬ 
tage  of  moisture  and  the  degree  of  compactness  of  sand  so  affects 
its  weight  per  cubic  foot  and  its  per  cent,  of  voids  that  weight  and 
void  determinations  are  of  no  practical  value  in  distinguishing  sands. 
An  illustration  of  the  variation  in  weight  and  volume  of  the  same 
sand  occurred  at  Jerome  Park  this  summer.  A  lot  of  Cowe  Bay 
sand  which  had  been  stored  in  the  laboratory  was  weighed  in  a 
measure  and  found  to  average  102.7  lb.  per  cu.  ft.,  the  weight  of 
three  determinations  being  respectively  103.6  lb.  101.8  lb.,  and 
102.8  lb.  As  the  sand  was  very  dry,  it  contained  38%  voids.  The 
same  sand  was  taken  out  of  doors  and  exposed  to  the  weather  for 
several  days.  A  storm  occurred  during  this  period.  Three  days 
after  the  rain  it  was  shoveled  into  a  measure  and  again  weighed, 
and  found  to  average  83.0  lb.  per  cu.  ft.,  three  weighings  giving 
82.9,  83.4  and  82.6  lb.  per  cu.  ft.,  respectively.  About  5%  of  this 
weight  was  moisture,  hence  the  air  voids  were  45.7%  and  the  air 
plus  water  voids  52.2  per  cent. 

Screening  Aggregate  in  Laboratory.  Barge  sieves  about  2  ft. 
square,  were  used  for  screening  the  aggregate  into  the  twenty-one  sixes. 
The  sieves  rested  in  a  frame,  one  above  another,  seven  to  a  frame, 
so  that  any  one  of  them  could  be  pulled  out  like  a  drawer  without 
disturbing  the  others.  The  frames  rested  upon  a  pair  of  rockers 
consisting  of  2-in.  plank,  sawed  with  angles  instead  of  rounding, 
so  that  the  motion  of  the  sieves  when  rocked  by  hand  was  a  com¬ 
bined  slide  and  jar.  Spikes  were  driven  into  the  rockers  at  the 


21 


angles  to  make  them  more  durable.  A  frame  of  sieves  and  a  single 
sieve  is  shown  in  the  background  of  the  photograph,  Fig.  8,  page 
38  and  sketched  in  Fig.  3  below. 

This  apparatus  worked  fairly  well,  although  difficulty  was  ex¬ 
perienced  in  getting  uniformity  of  screenings.  It  is  suggested  that 


Rear  View.  Section  of  Sieve 

Fig.  3.— Detail  of  Frame  for  Sieves  for  Screening  Aggregates  in  Laboratory. 

for  future  work  some  form  of  pedometer  be  placed  upon  the  frames 
to  record  the  number  of  shakes,  which  number  should  be  definitely 
fixed  for  each  series  of  sizes.  Each  lot  of  unscreened  material  placed 
in  the  top  sieve  of  each  series  should  be  measured  (as  this  is  suffi¬ 
ciently  accurate  and  requires  less  labor  than  weighing). 


22 


Diameters  of  Aggregate. — Experiments  have  shown  that  the 
diameter  of  the  largest  stone  passing  through  any  sieve  corresponds 
almost  exactly  to  the  width  of  the  opening.  The  method  of  rating 
is  referred  to  in  subsequent  paragraphs,  hut  it  may  be  said  in  gen¬ 
eral  that  the  diameters  of  the  stones  can  be  designated  by  the  width 
of  openings  in  the  wire  cloth.  The  usual  method  of  designating 
sieves  below  one-tenth  inch  diameter  is  by  a  commercial  number 
corresponding  to  the  number  of  meshes  in  a  linear  inch.  This 
hears  no  exact  relation  to  the  size  of  the  openings,  nor,  therefore,  to 
the  diameter  of  the  particles  passing  through  them,  because  of  the 
variation  in  the  size  of  the  wire  used  in  making  the  sieve.  Accord¬ 
ingly,  it  is  necessary  to  carefully  calibrate  wire  cloth  in  every  lot 
unless  it  comes  from  a  maker  who  has  adopted  standard  sizes  of  wire 
for  the  different  sieves.  The  Howard  &  Morse  Company  of  Brook¬ 
lyn  now  manufacture  wire  cloth  upon  a  standard  scheme,  so  that 
the  sizes  are  very  regular. 

The  diameters  of  sand  grains  in  the  diagrams  of  this  report 
are  designated  by  the  size  of  the  openings  in  the  sieve,  that  is,  by 
the  diameter  of  the  largest  particles  passing  through  it,  instead  of 
by  the  commercial  number  of  the  sieve.  The  diameters  of  par¬ 
ticles  with  the  corresponding  commercial  sieve  numbers  which  have 
been  adopted  in  this  series  of  tests  are  as  follows: 


TABLE  I. — Sizes  of  Sieves. 


Normal  sizes 
of  sieves, 
inches. 

Diameters 
passing  sieves, 
inches. 

Normal  sizes 
of  sieves, 
commercial 
number. 

Diameters 
passing  sieves, 
inches. 

2.25 

2.25 

10 

0.075 

1.50 

1.50 

15 

0.046 

1.00 

1.00 

20 

0.034 

0.75 

0.75 

30 

0.020 

0.60 

0.60 

40 

0.016 

0.45 

0.48 

50 

0.014 

0.35 

0.36 

74 

0.0071 

0.27 

0.29 

100 

0.0058 

0.20 

0.20 

150 

0.0036 

0.15 

0.16 

200 

0.0027 

0.10 

0.10 

Fig.  4.— Apparatus  Used  in  Volumetric  Tests. 


23 


The  number  of  sieves  adopted  is  so  large  as  to  require  consid¬ 
erable  time  and  labor  for  making  each  test.  It  may  be  possible  in 
future  experiments  to  omit  a  few  of  the  sizes,  if  tests  of  the  ma¬ 
terials  indicate  that  this  can  be  done  without  appreciable  effect  upon 
the  result. 

Methods  and  Apparatus  for  Determining  Density. 

Trial  mixes  of  aggregates  composed  of  various  sized  particles 
following  a  logical  plan,  and  containing  first  10%  of  cement  to  the 
total  weight  of  the  dry  materials  and  then  other  percentages  of 
cement,  were  made  and  mixed  with  water  to  the  same  medium  wet 
consistency,  and  the  resulting  volumes  thus  obtained  from  exactly 
the  saifie  total  weight  of  dry  materials  (corrected  for  specific  grav¬ 
ity)  were  compared.  The  tests  of  density  are  termed  volumetric  tests 
in  this  report.  The  general  procedure  (described  below)  in  making 
them  is  that  adopted  by  the  French  Commission,  in  1894,  and  the 
volumes  of  material  per  cubic  foot  were  calculated  by  methods  used 
by  Mr.  R.  Feret,  of  Boulogne-sur-Mer,  France,  in  his  determination 
of  elementary  and  of  absolute  volumes.  The  apparatus  used  in  the 
volumetric  tests  is  shown  in  the  photograph  in  Fig.  4,  page  22,  and 
the  apparatus  and  tools  are  sketched  in  Figs.  5  and  6,  on  pages 
25  and  27. 

Weighing. — All  materials  were  proportioned  by  dry  weight.  The 
natural  sand  and  screenings  as  they  came  from  the  pit  or  the  crusher 
were  dried  in  the  laboratory,  and  experiments  showed  that  after 
being  sifted,  they  did  not  collect  in  the  laboratory  a  sufficient  amount 
of  moisture  to  appreciably  affect  their  weights.  For  weighing  the 
materials  a  Fairbanks  scale  No.  1288,  with  compound  beam  having 
seven  scales,  was  employed.  The  scales  read  to  half  pounds,  and  by 
means  of  a  wire  rider  made  in  the  laboratory  it  was  possible  to  read 
to  hundredths  pounds,  although  the  accuracy  was  not  much  greater 
than  tenths.  In  the  density  tests  the  materials  were  weighed 
directly  in  the  mixing  pan  placed  upon  the  platform  of  the  scales. 
The  water  was  usually  weighed  in  a  16-quart  galvanized  iron  pail. 

Measuring. — For  measuring  the  volume  of  concrete  made  in  the 
volumetric  tests  an  old  cast-iron  air  brake  cylinder  and  piston  was 
found  convenient.  The  cylinder  was  8  in.  in  diameter  inside  meas¬ 
urement,  flanged  at  both  ends,  with  a  blank  flange  bolted  to  it,  thua 


24 


forming  a  vessel  8  in.  in  diameter  and  9  in.  deep.  This  vessel  was 
carefully  calibrated,  so  that  the  volume  of  the  contents  could  be 
obtained  by  measuring  down  from  the  top.  To  measure  the  depth  of 
concrete  and  thus  calculate  its  volume,  the  piston  was  set  in  the 
cylinder  on  top  of  the  concrete;  the  projecting  iron  rod  formed 
a  convenient  handle  and  also  provided  means  for  measurement.  A 
yoke  of  hard  wood  consisting  of  two  vertical  uprights,  connected 
by  a  crosspiece  at  the  top,  and  at  a  distance  apart  corresponding  to 
the  diameter  of  the  pipe,  was  made  to  place  upon  the  cylinder  and 
straddle  the  piston,  the  cross-piece  resting  against  the  handle  of  the 
piston.  These  are  all  shown  in  Tig.  4  and  are  sketched  in  Figs.  5 
and  6. 

A  mark  was  scratched  on  the  handle  of  the  piston  at  such  a  point 
that  for  any  position  of  the  piston  in  the  cylinder  the  distance  from 
this  mark  to  the  top  of  the  crosspiece  of  the  wooden  yoke  represented 
the  exact  distance  from  the  bottom  of  the  piston  to  the  average  sur¬ 
face  of  the  flange  forming  the  bottom  of  the  cylinder.  After  placing 
the  concrete  in  the  cylinder,  the  piston  was  pressed  down  upon  it 
until  its  bottom  surface  exactly  coincided  with  the  surface  of  the 
concrete.  The  depth  of  the  concrete  could  then  be  exactly  measured 
by  measuring  with  a  boxwood  scale,  reading  to  hundredths  of  inches, 
the  distance  between  the  mark  on  the  handle  of  the  piston  and  the 
top  of  the  crossbar  of  the  wooden  yoke.  From  this  depth  the  volume 
of  the  concrete  was  readily  calculated. 

The  larger  cylinder.  Fig.  6,  12  in.  in  diameter  and  18  in.  deep, 
was  made  for  volumetric  tests  of  materials  containing  large  size 
stone,  but  comparative  tests  with  this  and  the  smaller  cylinder 
showed  that  the  densities  obtained  by  the  two  apparatus  were  so 
nearly  identical  that  the  larger  one  was  not  used  to  any  great  extent. 

The  materials  were  proportioned  by  mechanical  analysis  curves, 
as  described  in  preceding  paragraphs,  and  the  weights  of  each  diame¬ 
ter  were  scheduled  from  these  curves.  The  mixing  pan,  which  was 
about  2  ft.  by  2  ft.  by  3  in.  deep,  was  placed  upon  the  scales,  and 
any  trowels  and  rammers  or  other  apparatus  to  be  used  in  the  opera¬ 
tion,  and  therefore  to  he  more  or  less  coated  with  cement,  were 
placed  in  the  pan,  and  the  weight  of  this  tare  recorded  on  one  of  the 
beams.  The  aggregates,  beginning  with  the  finest  diameter,  were 
then  weighed.  The  schedule  of  weights  of  the  aggregate  were  made 


25 


up  so  that  each  weight  included  the  weight  of  all  the  finer  aggre¬ 
gates.  In  this  way  the  weighing  poise  was  reset  for  each  size  of 
material,  and  the  materials  placed  in  the  pan,  one  on  top  of  the  other. 
The  cement  was  weighed  last,  so  as  to  be  on  top  of  the  other 
materials. 

Mixing. — The  mixing  was  done  by  two  men  working  on  opposite 
sides  with  large  trowels  and  turning  the  dry  material  until  of  uni¬ 
form  color,  in  the  same  manner  as  concrete  is  turned  by  hand.  The 
material  was  then  formed  in  a  ring,  water  poured  into  the  center, 


Fig.  5. — Tools  and  Tray  Used  in  Volumetric  Tests. 


and  the  mass  turned  until  the  mixing  was  thorough.  The  mixing 
pan,  trowels,  shovel  (in  plan  and  elevation),  cleaner  (in  plan  and 
section),  and  rammer  are  sketched  in  Fig.  5,  above. 

Because  of  the  variation  in  the  sizes  of  the  grains  of  the  aggre¬ 
gate  in  the  different  volumetric  mixes,  it  was  impossible  to  select  a 
definite  percentage  of  water  to  use  in  all  the  tests,  or  to  select  in 
advance  definite  percentages  for  each  mix.  The  mixtures  containing 
the  largest  quantities  of  very  fine  material  required  the  largest  per¬ 
centage  of  water.  A  series  of  volumetric  tests  of  mortars  made  with 
cement  and  sands  with  grains  of  different  size,  which  are  referred 
to  later  in  the  report,  was  started  in  order  to  study  the  reasons  for 


the  variation  in  quantity  of  water  required  under  different  condi¬ 
tions  and  to  formulate  some  rule  for  proportioning  it. 

The  water,  therefore,  was  added  by  judgment  to  obtain  a  soft 
mushy  mixture  which  would  scarcely  hold  its  form  in  the  mixing 
pan,  but  which  was  not  so  fluid  that  the  mortar  would  run  away  from 
the  stones.  A  pail  of  water,  with  its  dipper,  was  first  weighed,  as 
much  water  added  as  was  required,  and  the  weight  of  the  remaining 
quantity  deducted  from  the  original  weight  to  determine  the  net 
weight  used.  As  the  surplus  water  was  removed  from  the  specimen 
after  placing  in  the  cylinder,  the  quantity  finally  given  in  the  den¬ 
sity  sheets  represents  the  water  actually  contained  in  the  specimen 
as  it  began  to  set. 

Ramming. — The  mixed  concrete  was  introduced  into  the  cylin¬ 
der,  which  had  been  previously  weighed,  and  rammed  in  2-in.  layers. 
This  frequent  ramming  was  necessary  because  of  the  small  size  of 
the  receptacle,  the  friction  on  the  sides  preventing  the  material  from 
settling  even  with  very  wet  mixtures  if  ramming  was  delayed  until 
the  entire  amount,  which  averaged  a  little  over  6  in.  in  thickness, 
was  placed.  The  rammer  which  was  found  best  was  a  cast  iron  disc 
about  4  in.  in  diameter,  with  an  upright  handle,  sketched  in  Tig.  5. 

A  mixture  of  the  consistency  described  above  gave  the  best 
results  in  the  cylinder.  If  too  dry,  there  was  always  a  possibility 
of  occasional  large  air  voids,  and  it  was  more  difficult  to  manipu¬ 
late,  although  the  resulting  rammed  volume  was  about  the  same  as 
the  mushy  mix  which  was  used.  A  very  wet  mixture  did  not  work 
quite  so  well  as  either  the  mushy  or  the  dry,  the  mortar  probably  not 
being  in  a  sufficiently  plastic  condition  to  lubricate  the  stones. 
Rather  curiously,  a  very  wet  mixture  required  more  fine  material  to 
fill  the  voids  than  the  others. 

Removing  Surplus  Water. — As  the  concrete  was  rammed,  the  sur¬ 
plus  mortar,  if  there  was  any,  rose  to  the  surface,  and  the  water 
separated  forming  a  layer  from  |  to  l  in.  in  depth.  After  this  had 
become  clear,  it  was  removed  by  a  small  suction  pump,  and  the 
weight  deducted  from  the  weight  of  the  water  used  in  the  mix. 

Final  Weighing. — The  cylinder  containing  the  concrete  was 
weighed  as  a  check  upon  the  weights  of  the  dry  material  and  the 
water,  the  mixing  tray,  together  with  the  tools,  was  weighed,  and 
the  quantity  of  material  adhering  to  them  was  thus  found,  being 


27 


4  ' 


Level.  Bridge  used  on  smoill  cylinder. 

Fra.  6.— Apparatus  Used  in  Volumetric  Tests. 


28 


the  difference  between  this  weight  and  the  weight  of  the  clean  tray 
and  tools.  The  weight  of  the  portion  of  the  mix  adhering  was  intro¬ 
duced  into  the  final  calculations  as  described  below. 

Measurement. — After  the  surplus  water  was  removed,  care  was 
taken  to  see  that  the  surface  of  the  concrete  was  level,  with  no  pro¬ 
jecting  stones,  and  the  cylinder  was  leveled  by  placing  it  upon  a 
tripod  consisting  of  a  board  with  three  lag  screws  for  legs.  The  > 
piston  was  introduced  and  pressed  firmly  down,  but  not  with  suffi-  * 
cient  force  to  disturb  the  mortar  on  top  and  thus  force  it  up  between 
the  piston  and  the  side  of  the  cylinder.  The  wooden  yoke  wa&  I 
placed  in  position,  and  the  depth  of  the  concrete  in  the  cylinder 
measured,  as  described  above,  by  measuring  the  height  from  the  j 
top  of  the  yoke  to  the  mark  on  the  piston.  The  cylinder,  piston,  j 
yoke,  scale  and  magnifying  glass  are  shown  in  Fig.  6.  The  test  j 
was  now  complete  and  ready  for  computation,  the  records  having  ; 
been  entered  upon  the  blank  form  described  below.  The  concrete  ! 
was  thrown  away,  and  the  tools  cleaned  ready  for  the  next  experi-  j 
ment. 

Recording  and  Computing  Data. — The  form  for  recording  the  j 
data  in  the  volumetric  tests  of  concrete  is  given  on  the  following 
page,  in  Table  2,  with  a  typical  test  of  Cowe  Bay  material  recorded 
upon  it.  It  is  so  arranged  that  all  of  the  weights  may  be  entered  in 
the  laboratory,  and  the  printed  column  of  items  also  gives  the  con¬ 
stants  to  be  used  in  calculation  and  the  method  of  combining  the  j 
various  items  so  that  the  calculation  of  each  sheet  may  be  made 
by  rote  by  an  unskilled  computer.  The  experiments  in  each  class 
were  numbered  consecutively  for  convenience  in  reference.  The 
items  recorded  in  the  laboratory  were  the  weights,  and  the  depths  of  I 
piston  in  cylinder,  items  1  to  IT,  24,  34  to  40. 

The  weight  of  aggregate  finer  than  .0071  in.  diameter,  item  6, 
is  separated  from  the  weight  of  aggregate  coarser  than  this,  item  7, 
because  the  former  is  separately  used  in  subsequent  items  for  the 
calculation  of  the  material  adhering  to  the  tray  and  tools.  Item  8 
gives  the  weight  of  the  vessel  and  water  before  any  of  it  is  used  for 
mixing,  and  item  9  the  weight  remaining  after  mixing.  From  the 
difference,  item  10,  must  also  be  deducted  the  free  water  drawn  from 
the  surface  of  the  concrete,  item  17,  which  is  the  difference  between 
items  15  and  16,  and  also  the  weight  of  the  water  left  on  the  tray, 


29 


TABLE  2. 

The  Aqueduct  Commissioners,  N.  Y. 
Subject:  Concrete  Experiments. 
Blank  Form  for  Volumetric  Tests. 


City. 


File  No. 
Ac.  No. 
Sheet  No. 


iuted  by 


Checked  by .  Date,  Mar.  10,  1905. 


377£ 

3/10/05 


2.65 

.85 

21.50 


e . 

ninal  Mix. 

d  of  Cement . j  ^0iant 

ight . 

.  of  Aggreg.  finer  than  .0071' 

“  “  coarser  “  “ 

“  Vessel  +  Water  (1) .  29.00 

“  “  “  (2) . 27.40 

“  Water  Used .  1.60 

al  Wt.  Mixed .  26.00 

.  of  Tray  +  Tools  (2) .  13.15 

“  “  “  (1; .  13.08 

“  Mixed  Adhering . 07 

Syringe  +  W  ater .  2.62 

Syringe .  2.60 

Free  Water . 02 

Mix  Set  =  11—14—17 . 

1 0  v  1 4 

ter  left  on  Tray 


5  — |—  6  — i —  10 
Water  Set  =  10  —  17  — 19  • 
n  *  «  -  5  X  14 

Cement  “  =5 


26.51 

.02 


Aggreg. 
=  6  X 


finer 
6  X  14 
+ 


5  4-  6  +  10 
than  .0071  1 


1.58 

2.61 

.84 


5  + 


10 


23.  Net  Aggreg.  coarser  than  .0071 .  21.50 

24.  Depth  of  concrete  in  Cylinder,  in .  5.99 

25.  Vol.  of  concrete  in  Cylinder  in.,  .02934 

X  24  —  .001.... v . 174 

26.  Net  Water  per  cu.  ft.  as  mixed  „  .  9.2 


set 


Cement 


Aggreg. 1 


9.1 

15.0 


.128.4 


27 


Abs.  Vol.  Water  per  cu.  ft.  as  set  — 


Cement 


Aggreg. 


28_ 

194' 


165"  ‘ 


.146 

.077 


.778 

1.001 


“  “  Total  30  -j-  31  4-  32 . 

Wt.  of  Form  -f  Concrete . . .  77.23 

“  “  Form .  50,75 

“  “  Concrete . 26.48 

Temp,  of  Water .  40° 

Time  of  Mixing  after  Wetting . 

Remarks  on  Consistency . 


dARRs.— Looked  little  stony  in  mix.  Top  surface  filled.  No  excess  of  mortar  on  top.  Small 
No.  10,  right  under  top  surface. 


given  in  item  19,  thus  leaving  the  net  water  in  the  set  concrete  in 
item  20.  Figures  following  many  of  the  items  refer  to  the  numbers 
of  other  items;  the  fraction  following  item  19  represents,  for  exam¬ 
ple,  the  portion  of  the  mix  adhering  to  the  tray  and  tools  which  is 
water.  The  assumption  is  made,  the  fact  having  been  determined  by 
experiment,  that  the  mortar  sticking  to  the  tray  and  tools  consists  of 
cement,  and  particles  of  aggregate  finer  than  diameter  .0071,  and 
water.  The  weight  of  the  water  in  this  mortar  which  adheres  may 
be  found  from  the  proportion : 

Mix  adhering :  total  fine  mortar  =  water  in  mix  adhering :  total 
water.  Expressed  in  item  numbers,  this  becomes: 

item  14 

Item  19  =  item  5  +  itenUT+TtemlO  X  item  10- 

The  net  water  contained  in  the  concrete  is  thus  item  20,  which 
equals  item  10— (item  17  +  item  19). 


O' 


30 


The  net  weight  of  the  concrete,  item  18,  should  be  the  total  weight 
mixed,  item  11,  minus  the  mix  adhering  to  tray  and  tools,  item  14, 
minus  free  surface  water,  item  17.  This  item  18  should  coincide 
with  item  36  obtained  by  finding  the  net  weight  of  the  concrete  in 
the  pipe. 

The  net  weight  of  the  cement,  item  21,  is  the  weight  originally 
used  less  the  cement  adhering  to  the  tray  and  tools,  the  determina¬ 
tion  of  which  is  made  in  the  same  way  as  the  determination  of  the 
water,  item  19.  Item  22  is  similarly  calculated  to  determine  the 
actual  amount  of  aggregate  finer  than  .0071  left  in  the  concrete. 
As  no  aggregate  coarser  than  .0071  adheres  to  the  tray  and  tools, 
item  23  is  the  same  as  item  7. 

The  volume  of  concrete  in  cylinder  in  cubic  inches,  item  25,  is 
calculated  from  the  depth,  item  24,  by  multiplying  item  24  by  a 
coefficient  and  deducting  a  constant. 

The  weights  of  each  of  the  materials  per  cubic  foot,  items  26  to 
29,  are,  respectively,  the  quotients  of  the  total  net  weight  of  each 
material  divided  by  the  volume  of  the  concrete.  The  absolute  vol¬ 
umes,  items  30  to  32,  which  represent  the  total  volume  of  the  liquid, 
or  the  volumes  of  the  grains  of  cement  or  aggregate,  are  the  net 
volumes  per  cubic  foot  divided  by  the  specific  gravity  of  each  of  the 
materials.  These  absolute  volumes  represent  simply  the  ratios  of  the 
actual  volumes  of  each  ingredient  to  the  total  volume  of  the  con¬ 
crete. 


Proportioning  the  Ingredients  for  Maximum  Density. 

The  volumetric  tests  of  concrete  were  begun  in  1904.  In  the 
first  place,  it  was  the  aim  to  determine  for  the  various  materials 
under  consideration  artificial  mixtures  of  aggregates  of  diameters 
graded  by  methods  of  mechanical  analysis  already  described,  which 
would  give  concrete  of  maximum  density.  These  ideal  mixes  having 
been  determined,  the  concrete  made  from  them  could  be  compared 
with  respect  to  density,  strength  and  permeability  with  concrete 
made  from  simple  mixtures  of  natural  materials,  and  thus  the  best 
proportions  to  use  with  different  materials  upon  actual  construction 
work  could  be  fixed. 

The  larger  part  of  the  experiments  were  made  upon  the  same 
proportions  of  total  aggregate  to  cement.  The  tests  with  Jerome 


31 


Park  stone  and  screenings  for  the  most  part  were  with  10%,  by 
weight,  of  cement  to  the  total  dry  materials.  The  tests  with  Cowe 
Bay  sand  and  gravel  were  with  similar  proportions,  except  for  a 
slight  correction  for  the  difference  in  specific  gravity  in  order  that 
the  ratios  of  absolute  volumes  might  be  the  same.  In  the  earlier 
tests  mechanical  analysis  mixtures  were  made  to  definite  curves, 
such  as  parabolas  and  straight  lines  and  curves  intermediate  between 
these,  in  order  to  select  the  curve  giving  the  maximum  density.  In 
the  later  tests,  in  the  winter  of  1904-5,  the  methods  were  slightly 
changed  and  the  best  results  were  obtained  by  making  mixtures  on 
trial  curves  without  reference  to  their  mathematical  equations,  and 
then  having  found  the  best  curves,  equations  were  fitted  to  them,  so 
that  they  could  be  more  easily  applied  to  different  materials  and 
more  readily  plotted. 

All  the  earlier  density  specimens  were  found  to  be  inferior  to 
the  tests  made  at  Little  Falls.  Subsequent  results  in  the  manufac¬ 
ture  of  the  beams  indicated  that  this  was  due  to  the  quality  of  the 
cement,  which  has  already  been  referred  to  on  page  17.  From  the 
volumetric  tests  and  tests  of  the  composition  of  beams  of  neat 
cement,  it  appeared  that  the  difference  in  the  density  was  due  to  the 
cement  taking  so  much  water  in  gaging  that  the  volume  of  the  paste 
was  increased,  and  the  density  lowered.  In  the  winter  of  1904-5  the 
experiments  were  continued  with  the  cement  which  was  then  being 
furnished,  and  this  gave  satisfactory  results.  To  avoid  duplication 
of  tests  and  reach  conclusions  as  speedily  as  possible,  the  first  series 
of  experiments  in  the  winter  of  1904-5  was  made  with  one  class  of 
material,  broken  stone  and  screenings  excavated  from  Jerome  Park 
Reservoir  site,  and  with  10%  of  cement,  by  weight,  of  total  dry 
material.  This  was  followed  by  tests  with  Cowe  Bay  gravel  and 
sand  and  with  other  percentages  of  cement. 

Necessity  for  Using  Cement  in  Density  Tests. — The  necessity 
may  be  questioned  for  using  cement  in  the  tests  for  density,  which 
were  really  for  the  purpose  of  determining  the  best  proportions  of 
the  various  sizes  of  particles  of  the  aggregate.  Why  would  it  not 
have  been  simpler  to  use  only  the  dry  aggregate  with  no  cement  or 
water,  and  thus  more  readily  obtain  the  mixtures  which  would  give 
the  least  volume  with  the  same  weight? 

As  a  matter  of  fact,  both  theory  and  experiment  prove  that  the 


32 


mixtures  of  aggregate  which  give  the  greatest  density  dry  do  not 
necessarily  give  the  greatest  density  when  mixed  with  the  cement 
and  water.  The  cement  and  water  actually  occupy  space  in  the  mass, 
as  many  of  the  voids- are  too  small  for  the  grains  of  cement  to  fit 
into  them  without  expanding  the  volume,  and  the  water  surrounds 
the  grains  of  fine  sand  and  of  cement  and  actually  increases  the 
bulk.  As  an  illustration  of  this,  the  weight  per  cubic  foot  loose  of 
very  fine  sand,  if  weighed  absolutely  dry,  is  very  nearly  the  same 
as  the  weight  per  cubic  foot  of  a  very  coarse  sand  weighed  dry. 
However,  if  the  two  sands  are  mixed  with  cement  and  water,  the 
resulting  mortar  made  with  the  fine  sand  will  occupy  a  bulk  perhaps 
20%  greater  than  the  mortar  of  coarse  sand,  even  when  each  of  them 
is  mixed  with  the  cement  in  the  same  proportion  by  weight  or  by 
absolutely  dry  volume.  The  density  of  the  mortar  of  fine  sand  will 
be  correspondingly  less  than  the  mortar  of  coarse  sand.  Further¬ 
more,  the  proportion  of  cement  to  sand  affects  the  relative  bulk  and 
density  of  the  two  mortars,  1:1  mixtures  giving  different  compara¬ 
tive  results  from  1 :  4  mortars. 

If  fine  aggregate  having  grains  of  the  same  size  as  cement  par¬ 
ticles  were  used,  the  aggregate  could  have  been  mixed  with  water 
without  using  any  cement,  and  the  resulting  density  would  probably 
have  been  the  same  as  where  real  cement  replaced  the  fine  aggregate. 
However,  this  fine  aggregate  is  more  costly  than  cement  because  of 
the  labor  required  to  screen  it.  Moreover,  the  conditions  would 
not  have  been  so  practical  as  where  cement  itself  is  used. 

Density  Tests  with  2 \-in.  Jerome  Varh  Stone. — In  all  these  tests 
the  cement  was  included  in  the  mechanical  analysis  curve.  This 
was  in  accordance  with  the  assumption,  which  was  afterwards  proved 
to  be  correct,  that  the  grains  of  cement  acted  similarly  to  grains  of 
sand  of  similar  size  so  far  as  the  density  was  concerned.  A  trial 
mechanical  analysis  curve  was  drawn  based  on  previous  tests,  and  a 
volumetric  test  was  made  to  determine  the  density.  The  curve  was 
then  altered  in  various  ways  by  raising  and  lowering  it  at  different 
diameters  of  stone,  and  volumetric  tests  made  with  each  experi¬ 
mental  curve.  By  this  means  the  general  principles  of  the  density 
of  mixtures  of  Jerome  Park  broken  stone  and  screenings  with  10% 
Giant  Portland  cement  were  studied. 

The  curve  which  gave  the  best  result  when  using  a  graded  coarse 


33 


aggregate  with  the  cement  was  found  to  be  one  resembling  a  par¬ 
abola  in  appearance,  but,  more  strictly,  consisting  of  a  curve  having 
for  the  lower  portion  the  form  of  an  ellipse,  and  above  this  a  straight 
line  running  to  100%  on  the  maximum  diameter  of  the  stone,  in  this 
case  2i  in.  The  tangent  point  of  the  curve  and  straight  line  was 
at  about  0.2  in.  diameter.  The  curve  started  below  measurable 
diameters  on  the  7%  line,  indicating  that  at  least  7%  by  weight  of 
the  very  finest  diameters  of  particles  of  cement  or  sand,  or  both,  was 
required  for  a  dense  mixture. 

In  studying  these  density  curves,  the  attention  of  the  writer  was 
called  to  experiments  by  Mr.  A.  E.  Schutte,  for  the  Warren  Brothers 
Company,  Boston,  on  mixtures  of  aggregate  to  be  used  in  their 
bituminous  macadam  pavement.  Eor  this  class  of  work,  which  is 
really  a  scientifically  graded  concrete  with  bitumen  for  the  matrix 
instead  of  cement,  Mr.  Schutte  found  the  densest  mixtures,  and  the 
best  results  in  practice,  to  occur  when  a  large  percentage,  about  50% 
in  fact,  of  the  aggregate  consisted  of  the  coarsest  diameter  of  stone 
of  uniform  size.  Density  tests,  using  a  mixture  of  this  kind,  were 
made  at  Jerome  Park  for  comparison  with  the  tests  with  graded 
coarse  stone,  as  shown  in  Table  11,  page  65.  The  resulting  concrete 
was  found  to  be  slightly  denser  than  the  concrete  with  a  graded 
stone.  However,  the  mixture  did  not  look  so  well  in  the  mixing  pan, 
and,  while  no  doubt  with  a  plastic  substance  like  bitumen,  a  thor¬ 
ough  mixture  would  produce  excellent  results,  with  the  cement  there 
seemed  to  be  a  tendency  of  the  stones  to  separate  from  the  mortar 
more  than  with  the  concrete  containing  graded  coarse  stone. 
Whether  or  not  these  conclusions  would  apply  in  practice  has  not 
yet  been  determined.  Tests  of  beams  made  with  the  two  kinds  of 
mixtures,  although  somewhat  erratic,  indicated  a  scarcely  appreci¬ 
able  difference  in  the  strength.  Since  under  some  conditions  a  stone 
of  uniform  size  is  as  easy  to  obtain  as  a  graded  stone  or  “crusher 
run,”  further  experiments  are  desirable  to  compare  these  two 
methods  of  mixture,  and  to  prove  whether  under  some  conditions  the 
uniform  stone  may  not  be  economical.  This  matter  is  further  dis¬ 
cussed  on  page  63.  The  equations  of  the  curve  which  was  selected 
as  the  best  are  given  in  succeeding  paragraphs. 

Density  Tests  with  1-in.  and  \-in.  8tone. — The  best  analysis 
curve  for  cement  and  aggregates  whose  maximum  size  was  less  than 


34 


2i  in.  was  next  studied  in  a  similar  fashion,  using,  as  before,  10%, 
of  cement  to  the  weight  of  total  dry  materials.  The  curves  for  the 
smaller  stone  were  found  to  resemble  the  2^-in.  curve,  except  that  the 
tangent  began  at  a  smaller  diameter.  This  diameter,  where  the 
curve  ended  and  the  straight  line  began,  was  found  to  be  about  one- 
tenth  the  diameter  of  the  maximum  size  of  stone  used  in  the  mix¬ 
ture;  thus,  for  1-in.  stone,  the  tangent  point  was  at  about  0.1  in. 
diameter,  and  for  i-in.  stone  the  tangent  point  was  at  about  0.05  in. 
diameter.  This  suggested  the  possibility  of  a  curve  for  all  sizes  of 
stone  with  the  same  equation,  but  with  the  diameter  of  the  maximum 
size  as  a  function  of  one  of  the  terms.  It  was  found  that  the  shape 
of  the  curve  was  not  exactly  the  same  for  the  different  sizes,  but  by 
introducing  a  small  constant  in  the  values  of  the  axes  of  the  ellipses, 
an  equation  was  found  which  fitted  all  the  diameters. 

Cement  vs.  Fine  Sand. — The  experiments  just  described  assume 
that  so  far  as  density  is  concerned,  cement  acts  in  the  same  way  as 
sand  with  grains  of  the  same  size.  The  cement  was  therefore  in¬ 
cluded  in  making  up  the  mechanical  analysis  curve.  To  prove  this 
assumption,  several  other  percentages,  ranging  from  8  to  15%,  of 
cement  to  weight  of  total  aggregate  were  tried,  using  the  best  curve 
already  found  for  the  mixtures  with  10%  of  cement,  and  the  result¬ 
ing  densities  were  substantially  identical  with  the  density  of  the 
mixture  by  the  same  curve  using  10%  cement.  It  is  evident  from 
this  that  correct  proportioning  for  concretes  of  maximum  density, 
but  of  different  strength,  consists  in  not  simply  increasing  the  per¬ 
centage  of  cement,  if  a  richer  mixture  is  required,  but  substituting 
more  cement  for  a  like  absolute  volume  of  sand  having  grains  of  the 
same  size  as  the  cement.  In  other  words,  the  larger  the  proportion 
of  cement,  the  less  very  fine  grains  of  sand  are  required,  because  the 
cement  takes  the  place  of  them  in  increasing  the  density. 

Density  Tests  with  Cowe  Bay  Material. — Tests  of  density  of  con¬ 
crete  composed  of  cement  and  of  gravel  and  sand  from  Cowe  Bay 
were  made  in  a  similar  manner  to  those  of  cement  and  Jerome  Park 
stone  and  screenings.  This  investigation  is  of  interest  not  only  with 
reference  to  the  work  at  Jerome  Park,  but  to  throw  light  on  the 
mooted  question  of  the  relative  value  of  broken  stone  and  gravel,  and 
form  some  basis  for  an  economical  comparison  of  the  two  in  any 
given  locality.  Relative  results  are  tabulated  in  Tables  8  and  9, 
pages  60  and  62. 


35 


Tests  were  made  with  concrete  composed  of  straight  Cowe  Bay 
material,  that  is,  gravel  and  sand  and  cement,  and  with  concrete  of 
Jerome  Park  broken  stone,  Cowe  Bay  sand  and  cement.  The  best 
curves  for  both  of  these  combinations  were  found  to  be  similar  to  the 
curves  for  concrete  with  straight  Jerome  Park  material,  except  that, 
because  of  their  rounded  nature,  the  particles  packed  more  closely 
together,  so  that  similar  mixtures  gave  with  the  Cowe  Bay  material 
a  greater  density,  and  for  maximum  density  a  smaller  quantity  of 
fine  material  was  required,  the  curves  in  the  diagram  for  Cowe  Bay 
material  being  lower  on  the  ordinate  corresponding  to  one-tenth  the 
maximum  diameter  of  the  stone.  The  combination  of  Jerome  Park 
stone  and  Cowe  Bay  sand  required  more  fine  material  than  the 
Cowe  Bay  gravel  and  sand,  but  less  than  the  Jerome  Park  stone  and 
screenings. 

Ideal  Sand. — The  character  of  the  best  or  ideal  sand  does  not 
appear  to  depend  upon  the  character  of  the  coarse  aggregate,  the  best 
sand  for  Jerome  Park  broken  stone  also  being  found  best  for  the 
Cowe  Bay  gravel  of  the  same  sized  grains,  although  less  was  re¬ 
quired  with  the  latter.  On  the  other  hand,  the  curve  for  the  Jerome 
Park  screenings  (plus  cement)  was  slightly  different  from  the  Cowe 
Bay  sand  (plus  cement)  curve,  showing  a  different  arrangement  of 
grains. 

Equations  of  Ideal  Mechanical  Analysis  Curves. 

Having  found  by  trial  the  curves  for  the  best  analyses  of  each  size 
and  class  of  material,  mathematical  curves  were  fitted  to  them  for 
convenience  in  plotting.  As  already  stated,  all  the  curves  for  aggre¬ 
gate  plus  cement  consist  of  ellipses  with  straight  lines  tangent  to 
them.  The  curves  all  start  upon  and  are  tangent  to  the  vertical  zero 
axis  of  percentages  at  7 % — that  is,  at  least  7%  of  the  aggregate  plus 
cement  is  finer  than  the  Ho.  200  sieve — and  run  as  ellipses  with  axes 
differing  with  the  character  of  the  materials,  to  a  point  which  was 
found  to  be  on  a  vertical  ordinate  or  diameter  whose  value  is  about 
one-tenth  the  diameter  of  the  maximum  particles  of  stone,  and 
thence  by  a  tangent  to  the  ordinate  of  maximum  diameter,  intersect¬ 
ing  this  on  the  100%  abscissa. 

The  general  equation  of  all  the  ellipses,  using  their  own  axes,  is 

&2  _ 

y  =  ‘I"  a2  V a2  —  x2- 


36 


Suisswa;  s^uaoaaj 


Fig.  7.— Diagram  of  Ideal  Curves  for  Mixing  Concrete  of  Various  Sized  Aggregates. 


37 


This  is  the  simplest  equation  to  use  for  plotting,  as  it  is  in  regular 
form,  and  only  the  values  of  a  and  b,  that  is,  the  major  and  minor 
axes,  are  required.  Using  zero  coordinates  on  the  mechanical  analy¬ 
sis  diagram,  the  equation  becomes 

(: v  —  02  =  (a  x — *2)- 

The  values  of  a  and  b  for  the  different  materials  (plus  cement)  used 
are  as  follows : 


Materials.  a. 

Jerome  Park  Stone  and  Screenings.  .  .035  -f-  .14  D 

Cowe  Bay  Gravel  and  Sand . 04  +  .1' 6  D 

\ Jerome  Park  Stone  and  Gowe  Bay 

Sand  . 04  +  .16  D 


b. 

29.4  +  2.2  D 

26.4  +  1.3  D 

28.5  +  1.3  D 


In  this  table  D  =  the  maximum  diameter  of  the  stone  in  inches. 
The  numerical  values  for  these  with  different  sizes  of  stone  are 
given  in  Table  6  on  page  50. 

Directions  for  Plotting  Ellipses. — In  practice  the  ellipses  are 
plotted  graphically  by  the  trammel  point  method  as  follows : 

^  Plot  the  major  and  minor  axes  on  the  diagram.  The  major  or 
liorizontal  axis  in  all  cases  is  on  a  line  7%^  above  the  base.  The 
niinor  or  vertical  axis  is  at  a  distance,  a,  to  the  right  of  the  vertical 
zero  ordinate  of  the  diagram.  Lay  a  strip  of  paper  or  a  thin 
straight-edge  upon  the  major  or  horizontal  axis,  and  mark  upon  it 
two  points  to  represent  the  length  of  the  semi-major  axis,  calling  one 
of  these  points — the  point  on  the  zero  ordinate — 0 ,  and  the  other 
point  A.  Mark  off  on  the  strip  or  straight-edge,  in  the  same  direc¬ 
tion  from  0,  the  length  of  the  semi-minor  axis,  calling  this  point  B. 
Mow,  swing  the  strip  of  paper  or  straight-edge  little  by  little  so  that 
the  outline  of  the  curve  may  be  marked  off  by  the  point  0,  while  the 
points  A  and  B  are  kept  at  all  times  upon  the  axes  b  and  a  re¬ 
spectively.  The  straight  lines  to  continue  the  curves  are  drawn  as 
tangents  to  them,  or  may  be  readily  plotted  from  the  data  in  Table  6. 

Diagram  of  Ideal  Curves. — The  ideal  curves,  that  is,  the  best 
curve  for  each  material  and  each  size  of  material,  are  plotted  in  the 
diagram,  Fig.  7,  page  36, 


38 


Methods  and  Apparatus  for  Beams. 

The  method  of  weighing  the  materials  for  the  beams  and  mixing 
them  was  similar  to  the  processes  in  the  volumetric  tests  for  density 
of  concrete.  The  tools  and  various  implements  used  in  making  the 
beams  are  shown  in  the  photograph  in  Fig.  8,  opposite. 

Weighing. — The  weight  of  each  diameter  of  aggregate  and  of 
cement  was  calculated  by  direct  proportion  from  the  percentage 
curve,  and  the  approximate  quantity  of  water  to  use  estimated  from 
the  quantity  employed  in  the  volumetric  tests  made  with  materials 
of  the  same  mechanical  analysis.  The  total  quantity  of  dry  mate¬ 
rials  for  a  beam  6  in.  by  6  in.  by  72  in.  varied  appreciably  with  the 
maximum  size  of  stone  and  with  the  character  of  the  material.  The- 
larger  the  stone,  the  greater  the  weight  of  material  required  for  a 
beam,  because  of  the  greater  density.  The  Cowe  Bay  material  has 
lower  specific  gravity  than  the  Jerome  Park  stone  and  screenings,  so 
that  a  less  weight  was  required  on  this  account,  but  the  density  of 
the  resulting  concrete  was  greater,  so  that  this  nearly  balanced  the 
other.  The  quantity  for  a  mixture  with  1 :  9  proportions  by  weight 
averaged  about  220  lb.  of  aggregate  and  25  lb.  of  cement.  The 
weights  actually  used  for  each  beam  may  be  directly  figured  from 
the  data  in  Tables  14a  to  14e,  pp.  105  to  109,  following  page  72. 

The  can  for  receiving  the  material,  about  18  inches  in  diameter 
by  2  ft.  deep,  was  placed  on  the  scale  and  the  tare  recorded  by  the , 
weigher.  Two  other  men  scooped  the  different  sizes  of  aggregates 
beginning  with  the  finest,  and  also  the  cement,  into  the  can,  the 
poise  being  slid  ahead  for  each  size. 

Mixing. — The  dry  material  was  then  dumped  upon  the  mixing 
platform,  which  was  5  by  8  ft.  and  made  chiefly  of  a  plate  of  sheet 
iron  surrounded  by  a  strip  of  wood  to  prevent  the  soft  material  from 
overflowing.  Four  men  turned  the  dry  material  with  square  pointed 
shovels,  just  as  hand-mixed  concrete  is  turned  in  practice.  Three 
turnings  were  given,  dry.  The  stuff  was  formed  into  a  circle,  when 
the  approximate  amount  of  water  was  weighed  and  turned  into  it. 
The  material  was  then  mixed  wet  by  the  four  men,  as  in  practice. 
Three  turnings  were  given  to  it  to  insure  a  uniform  mix  throughout 
the  beam. 

Consistency. — The  required  consistency  was  soft  and  mushy,  but 
not  wet  enough  for  the  mortar  to  run  away  from  the  stones,  scoop 


Fig.  8.— Implements  Used  in  Making  Beams. 


39 


shovels  being  necessary  to  handle  the  wet  concrete.  If  the  calculated 
weight  of  water  was  not  sufficient  to  give  the  required  consistency, 
more  was  added  and  the  weight  of  it  recorded. 

Marks  for  Specimens. — Four  marks  were  imbedded  in  each  beam. 
The  tags  consisted  of  pieces  of  brass  stamped  by  hand  by  a  die 
with  the  number  of  the  beam  and  followed  by  the  letters  A,  B,  C  and 
D  respectively.  Each  tag  was  about  1|  in.  long  by  i  in.  wide,  and 
had  projections  bent  up  from  it  to  run  into  the  concrete.  They  were 
definitely  located  in  the  bottom  of  the  mold  by  measurement,  so  as 
to  lie  nearly,  but  not  quite,  in  the  center  of  each  of  the  four  pieces 
into  which  the  beam  was  finally  broken.  Each  tag  was  placed  in  the 
bottom  of  the  mold,  and  held  with  the  blade  of  a  shovel  until  the 
concrete  was  poured  around  and  on  top  of  it,  thus  holding  it  in 


*llron  Casf/ng 

Plan.  Section. 


Fig.  9.— Sketch  of  Moulds  Used  for  Making  Concrete  Beams. 

place.  The  tags  were  often  slightly  covered  by  thin  mortar  which 
ran  under  them,  but  being  exactly  located,  they  were  readily  found 
by  scraping  the  surface. 

Placing  in  Molds. — The  mold  for  the  beam,  shown  in  Fig.  9, 
above  was  weighed  and  the  concrete  shoveled  into  it,  and  placed 
and  slightly  compacted  with  the  aid  of  large  trowels  and  shovels. 
The  blade  of  a  shovel  was  generally  thrust  down  by  the  faces  of  the 
forms  to  insure  a  smooth  surface,  although  this  was  not  found  abso¬ 
lutely  necessary.  The  mold  with  the  concrete  was  weighed  to  obtain 
the  weight  of  concrete  green  for  density  determination,  and  placed 
one  side  to  set. 

The  quantity  of  material  required  had  been  approximately  calcu¬ 
lated  from  the  volumetric  tests.  If  any  was  left  over,  after  the  mold 


40 


was  filled,  it  was  weighed  and  the  proportion  of  this  which  was 
water  was  estimated.  As  the  proportional  amount  of  water  may 
exert  a  difference  of  2  or  3%  upon  the  calculated  density  of  the 
beam,  it  is  suggested  that  in  future  tests  the  concrete  left  over  be 
carefully  separated  from  the  excess  water,  so  as  to  have  about  the 
same  consistency  as  the  beam,  and  then  weighed,  while  the  water 
remaining,  together  with  the  free  water  from  the  surface  of  the  con¬ 
crete  in  the  mold,  be  separately  weighed  and  recorded.  As  this 
water  contains  some  cement  in  suspension,  its  approximate  specific 
gravity  should  be  determined  by  a  test,  and  this  specific  gravity  used 
in  the  calculations  of  the  density  of  the  beams. 

As  soon  as  the  concrete  was  hard  enough  to  handle  easily,  which 
was  usually  in  about  7  days,  it  was  buried  in  moist  sand,  where  it  I 
remained  until  the  date  of  test. 

Recording  and  Computing  Data  on  Beams. — The  method  of  re¬ 
cording  the  data  for  mixing  is  given  in  Table  3.  The  form  is  filled 

TABLE  3. — Form  for  Mixing  Beam  Material. 


Wt.  of  Form  No.  14  empty . .  131.25 

••  “  “  filled .  364.00 

“  “  Beam  217  . 232.75 

Total  Wt.  mixed . 234.00  | 

Wt.  of  Mix  left  over .  0.00 

Total  Wt.  of  Beam . 232.75 

Wt.  unaccounted  for . 1.25 

Wt.  of  Form  No.  14  filled . 359.75 

Beams  buried— day,  hour,  days  be-|  o/on/nA 
fore  burying . \  3/<5b/U4 

Loss  of  wt.  in  setting  .  7 

Inspector,  W.  H. 


out  with  a  typical  test  for  illustration.  When  ready  to  break,  after 
removing  from  the  moist  sand,  measurements  are  taken  for  the  pur¬ 
pose  of  figuring  the  density  and  calculating  the  modulus  of  rupture. 
The  form  for  this,  with  typical  measurements  filled  out,  is  given  in 
Table  4,  on  page  41.  As  each  beam  was  broken  into  four  pieces, 
first  in  the  middle,  and  then  the  two  halves  broken  again,  measure¬ 
ments  were  taken  at  half  and  quarter  points,  also  at  the  two  ends, 
making  five  sections  in  all.  At  each  section,  three  dimensions  were 


No.  of  Beam . 217 

Approx.  Vol.  of  Beam . 1J4  cu.  ft. 

Date . May  21,  1905. 

Hour . 1.30  p.  m. 

Temp,  air  in  cellar . 64° 

Kind . 

Lot  No . 

Wt.,  lbs . 

Cement. 

. 23.32 

Kind . 

Analysis  No. . 
Wt.,  lbs . 

Aggregate. 

. Ideal  36%  ord. 

Temp.  F . 

Total  used . . . . 

Water. 

. 54° 

. . . 14.0 

Fig.  10.— Machine  for  Breaking  Beams. 


41 


measured  of  depth  and  three  of  width.  The  beams  were  placed  in 
the  machine  on  their  side,  and  therefore  the  depth  as  measured  is 
really  the  width  of  the  beam  in  the  mold,  and  the  width  as  measured 
is  the  height  of  the  beam  in  the  mold.  As  the  quarters  are  labelled 
with  the  number  of  the  beam  followed  by  A,  B,  C  and  D,  respectively, 
the  measured  sections  are  A,  AB,  BC,  CD,  and  D.  Upon  each  beam, 
thirty  sectional  measurements  are  thus  made,  each  reading  to  hun- 


TABLE  4. — Eorm  for  Dimensions  of  Beams. 


Number  of 
Beam. 

Section 

Letter. 

Depth  (Inches). 

Width  (Inches). 

Area. 

Av. 

Area. 

Length 

(Inches). 

Contents, 

cu.  ft. 

Side. 

Mid. 

Side. 

Av. 

Side. 

Mid. 

Side. 

Av. 

f 

A 

6.01 

5.94 

5.98 

5.98 

6.09 

6.00 

5.98 

6.02 

36.00 

1 

1 

AB 

6.01 

6.03 

6.07 

6.04 

6.05 

6.00 

6.00 

6.02 

36.36 

166  ■{ 

BC 

6.02 

6.00 

6.00 

6.01 

6.15 

6.17 

6.12 

6.15 

36.96 

>■36.10 

72 

1.504 

\ 

CD 

5.97 

5.95 

5.98 

5.97 

6.02 

6.02 

5.85 

5.96 

35.58 

| 

l 

D 

6.03 

6.00 

6.01 

6.01 

5.89 

5.95 

1 

5.91 

5.92 

35.58 

J 

dredths  of  inches.  From  the  beam  mixing  data  and  the  calculated 
volume  of  the  beam,  the  weights  of  the  material  in  one  cubic  foot  of 
the  beam  and  the  absolute  unit  volumes  are  calculated.  The  modu¬ 
lus  of  rupture  for  each  break  is  calculated  from  the  dimensions  and 
the  breaking  weight. 

Beam  Testing  Machine. — The  machine  for  breaking  the  beams 
was  made  by  Riehle  Brothers,  Philadelphia,  and  the  method  of 
loading  it  improved  in  the  laboratory.  A  photograph  of  the  machine 
with  a  beam  in  place  ready  to  break  is  shown  in  Fig.  10,  page  40. 
In  order  to  avoid  the  negative  moment  due  to  overhanging  portions 
of  the  beam,  the  bearings  for  each  specimen  were  2  inches  from  each 
j  end  of  the  beam,  thus  giving  a  variable  length  between  supports  for 
i  specimens  of  different  length,  but  a  overhang  so  short  as  to  be  neg- 
!  ligible  in  the  calculation.  Instead  of  using  the  poise  for  weighing 
\  the  load  upon  the  beam,  an  attachment  was  designed,  as  shown  in 
the  top  of  the  photograph,  so  that  the  beam  was  loaded  by  dropping 
!  shot  from  a  tin  funnel  into  a  vessel  suspended  from  the  scale  beam. 
This  avoided  the  irregularities  incident  to  the  machine  as  furnished 
by  the  manufacturers. 


I 


42 


Compression  Pieces. 

As  there  is  no  constant  relation  between  the  transverse  modulus 
of  rupture  of  concrete  and  the  compressive  strength  of  the  same  mix¬ 
ture,  a  scheme  was  devised  for  obtaining  the  compressive  strength 
of  all  of  the  mixtures  in  addition  to  the  transverse  modulus  of  rup¬ 
ture.  After  breaking  the  beams  into  four  pieces,  the  two  end  pieces 
were  capped  with  neat  cement  so  as  to  form  prisms  about  6  inches 
square  and  19  inches  long.  The  method  of  capping  these  prisms  is 
illustrated  in  the  drawing  in  Pig.  11,  below.  Two  pieces  were 


;/7gy/<g  .Q/C/SS  6 "x  !0'k  Boaro/  /4  “x  //  ^ 


r 

V  • 

C/amp  dL6" Lonq 

Block— 

/Z"x6'k/0‘‘ 

QraCZ 

S  \ 

——A - 

i 

— — - 

< 

Fl 

|  \  ^  Board  n  6'x  /3"-^  Block  fZ’x&'x/O? 

P  lot  n. 


S>iote  ELIevort ion. 

Fig.  11.  —Sketch  Showing  Method  of  Capping  Test  Prism  for  Compression. 

capped  at  the  same  operation.  A  piece  of  smooth,  planed  2-in.  plank 
was  laid  upon  horses,  and  upright  upon  this,  in  a  wooden  frame,  were 
set  four  pieces  of  i-in.  plate  glass,  each  6  in.  by  10  in.  The  lengths 
of  the  prisms  were  gaged  by  boards  1  by  6  by  19  in.  placed  length¬ 
wise  and  6  in.  apart,  so  that  the  broken  piece  of  the  beam  fitted  be¬ 
tween  them  with  a  space  at  each  end  between  the  rough  ends  of  the 
beam  and  the  plate  glass.  The  pieces  of  beams  were  thoroughly 
soaked  with  water  before  beginning  the  operation.  A  plastic  paste 
of  neat  cement  as  stiff  as  could  be  readily  handled  and  molded 


43 


was  next  worked  into  the  spaces  between  the  ends  of  the  specimen 
and  the  plate  glass,  and  allowed  to  set  over  night.  When  removed 
from  the  mold,  each  prism  was  capped  with  neat  cement  with  a 
smooth,  glossy  surface,  and  the  two  ends  were  parallel.  These 
prisms  were  sent  to  Stevens  Institute,  at  Hoboken,  and  broken  in 
the  compression  machine.  Certain  ones  were  tested  there  also  for 
elasticity. 


Comparative  Compressive  Strength  of  True  Prisms  vs.  Capped 
Pieces  of  Beams. 

The  question  naturally  arose  whether  the  strength  of  prisms 
capped  with  neat  cement  in  this  way  corresponds  to  the  true  com¬ 
pressive  strength  of  the  concrete.  The  neat  cement  capping,  which 
was  of  different  thickness  in  the  different  specimens,  might  affect  the 
strength,  and  the  specimens  might  be  strained  from  the  rupture  in 
the  transverse  tests.  In  order  to  compare  the  strength  of  the  capped 
pieces  with  the  true  prisms,  one  of  the  beam  mixtures  was  used  for 
making  up  four  prisms  6  in.  by  6  in.  by  18  in.,  and  these  true  prisms 
were  broken  at  the  same  age  as  the  capped  pieces  of  beams  mixed 
with  the  same  ingredients  in  like  proportions.  The  results  of  this 
comparison  are  shown  in  Table  5,  below.  It  is  noticeable  that  the 

TABLE  5. — Compressive  Strength  of  True  Prisms,  6  X  6  X  18 
Inches,  vs.  Capped  Pieces  of  Same  Dimensions  from  Broken 
Beams,  1 : 9  Concrete,  with  Graded  Jerome 
Park  2|-in.  Aggregate. 


True  Prisms. 


Capped  Pieces  of  Beams.* 


Reference 

No’s. 

Compressive 
strength, 
lbs.  per 
sq.  in. 

Variations 
from  mean. 

Reference 

No’s. 

Compressive 
strength, 
lbs.  per 
sq.  in. 

Variations 
from  mean . 

161 

1  375 

93 

155 

1  580 

153 

161 

1  240 

42 

155 

1  450 

23 

161 

1  235 

47 

155 

1  250 

177 

162 

1  330 

48 

157 

1  490 

63 

162 

1  315 

33 

157 

1  485 

58 

162 

1  195 

87 

157 

1  305 

122 

Average . 

1  282 

58 

Average . 

1  427 

99 

Per  Cent . 

4.5 

14.4 

-  - 

| L. 

*  The  Compression  Tests  in  the  other  Tables  are  made  upon  the  capped  pieces  of 


44 


capped  prisms  give  a  higher  average  strength  than  the  true  prisms, 
and  there  is  greater  variation  between  the  different  specimens.  The 
variation,  however,  is  not  so  great  but  that  the  results  from  the 
capped  pieces  is  of  value,  at  least  when  used  in  connection  with  the 
values  of  transverse  strength.  In  the  tables  which  follow,  the  com¬ 
pressive  strength  of  these  capped  prisms  is  therefore  given  side  by 
side  with  the  transverse  strength  and  the  density.  The  full  results 
of  the  compressive  tests  are  also  given  in  Tables  14  a  to  e. 

1904  Beam  Tests. 

The  first  series  of  tests  of  beams  were  made  in  the  winter  of 
1903-4.  The  materials  were  Portland  cemenl  crusher-run  screen¬ 
ings  brought  directly  from  the  crusher  in  the  reservoir  without 
laboratory  screening,  and  crusher-run  broken  stone  also  brought 
directly  from  the  crusher  after  there  sifting  out  the  screenings  in 
the  revolving  screens.  The  results  of  the  tests  are  somewhat  erratic 
and  the  breaking  strengths  are  low,  because  of  the  peculiarity  of  the 
cement,  to  which  reference  has  already  been  made.  The  concrete 
set  very  slowly,  and  had  to  be  stored  in  the  mold  for  two  or  three 
weeks  before  the  beams  could  be  handled  without  breaking. 

In  the  diagram,  Fig.  12,  curves  of  equal  modulus  of  rupture  are 
drawn  as  contours  interpolated  between  the  plotted  breaking- 
strengths  as  found.  Notwithstanding  the  apparently  poor  results 
of  the  tests  and  the  relatively  low  breaking  strength,  the  curves  fol¬ 
low  the  same  general  direction  as  those  of  the  tests  at  Little  Falls, 
N.  J.,  made  in  1901,  with  broken  trap  rock  and  sand,  although  the 
strength  of  similar  mixtures  is  less  at  Jerome  Park.  Fig.  13,  page 
45,  gives  curves  showing  the  weight  of  cement  in  pounds  in  1  cu. 
ft.  of  the  set  concrete  in  the  beam.  These  results  also  agree  closely 
with  those  at  Little  Falls  except  that  the  latter  contain  more  cement 
per  cubic  foot  of  set  concrete  than  the  same  proportions  at  Jerome 
Park. 

1905  Beam  Tests. 

As  a  result  of  volumetric  tests  of  density  carried  on  in  the  spring 
and  winter  of  1904,  the  concrete  beams  in  1905  were  made  according 
to  definite  plans  to  compare  the  strength  of  concrete  made  with 
different  materials  and  different  proportions  of  the  various  diameters 
of  particles.  Cement  and  aggregate,  graded  by  curves  of  mechanical 


45 


ttodu/us  of  Rupture  of  Concrete  Beams, Gincbes  5quane-30and 60  Span-  tbundj perSquore  inch, 
fbrts  of  Stone,  by  Weight. 

0  I  2  3  A  5  6  y  8  9  /O  II  /2  /j  ,q 


\  > 

\ 

Data  from  Tests  at  Jerome  Park  Reservoir N.  Y,  1904. 

Aqueduct  Commission 

Gian  t  Cement,  Jerome  ParRScrveninqs  used  assart? 
Jerome  ParRS/oneiz" To  2/4 

Concrete  mixed  very  wet. 

Yr 

.  0  /  Z  3  -f  5  6  7 

Fig.  12 


Weight  of  Cement,  in  Pounds, Required  in  One  Cubic  Foot  of  Concrete. 
Parts  of  Stone,  by  Weight. 


I 

I 

V. 

| 

<5 


\ 

X 

/ 

9 

'0 

// 

/2 

' 3  / 

y 

'  X 

\ 

X 

\ 

\ 

\ 

data  from  tests  at  Jero/t/e  Part 
Agueducf  Comm 

'Reserve 

'ission 

vrNXRi 

m 

0  / 

2 

:  3 

\  ' 

4 

A 

r  ^ 

y 

G/ant  Ce/nent,Jero/ne  fbrp Screenings  usee/ os  sand. 
Jerome  Park;  Stone  t"  1o  2.±" 

Concrete  mixed  very  n/et. 

Fig.  13. 


46 


analysis  which  we're  found  by  the  volumetric  tests  to  produce  con¬ 
crete  of  maximum  density  for  a  given  kind  of  material,  were  used 
as  a  basis  for  the  tests.  The  strengths  of  these  ideal  specimens  were 
then  compared  with  the  strengths  of  concrete  mixtures  proportioned 
by  the  artificial  mechanical  analysis  curves  which  in  the  volumetric 
tests  showed  less  density,  to  establish  the  general  law  that  with  the 
same  percentage  of  cement  the  densest  concrete  is  the  strongest;  the 
strengths  of  these  ideal  mixtures  were  compared  with  the  strength  of 
mixtures  of  natural  material  in  ordinary  proportions,  and  also  in 
the  best  possible  natural  proportions;  the  relative  strengths  of  con¬ 
cretes  made  with  stone  of  different  maximum  size  were  compared; 
the  relative  strengths  of  concrete  made  with  Jerome  Park  stone  and 
screenings  were  compared  with  Cowe  Bay  gravel  and  sand  and  with 
Jerome  Park  stone  and  Cowe  Bay  sand;  and  the  comparative 
strengths  of  neat  cement  and  concrete  beams  made  with  different 
brands  of  cement  were  tested. 

The  beams  were  broken  in  the  beam  machine  into  four  pieces, 
and  two  of  the  end  pieces,  as  already  has  been  described,  were  capped 
with  neat  cement  for  compression  tests,  some  of  these  specimens 
being  also  tested  for  elasticity.  One  piece  each  from  twenty-seven 
beams,  selected  so  as  to  show  relative  results,  was  tested  for  permea¬ 
bility,  as  described  in  subsequent  pages. 

When  a  series  of  tests  was  commenced  full  instructions  were 
typewritten,  so  that  the  experiments  could  proceed  in  the  laboratory 
without  direct  supervision.  It  was  intended  that  two  beams  should 
be  made  of  each  mixture,  each  beam  being  separately  manufactured, 
however,  in  order  that  the  exact  weights  of  materials  entering  into 
it  could  be  determined.  In  certain  cases  it  was  found  expedient  to 
make  only  one  beam  of  a  mixture,  but  the  results  with  these  speci¬ 
mens  were  not  so  good,  three  transverse  breaks  and  two  compressive 
breaks  not  being  sufficient  to  give  a  fair  average  of  the  material. 
The  full  list  of  tests,  of  which  there  were  116  specimens  in  all,  are 
briefly  scheduled  as  follows: 

Straight  Jerome  Park  material,  using,  respectively,  2f-in.,  1-in. 
and  i-in.  stone,  mixed  with  screenings  and  10%  cement,  by  weight, 
to  total  dry  materials,  and  graded  to  the  best  ideal  curves  for  each 
size,  and  to  other  artificial  curves  having  more  sand  and  less  stone 
than  the  ideal. 


47 


Straight  Jerome  Park  material,  using,  respectively,  2|-in.,  1-in. 
and  1-in.  stone,  mixed  with  screenings  and  cement  in  three  natural 
proportions — 1 :  21 :  61,  1:3:6,  and  1:31:  51. 

Straight  Jerome  Park  material,  using  for  the  coarse  aggregate, 
stone  of  uniform  size,  21-in.,  1-in.  and  1-in.  diameter,  respectively, 
mixed  with  screenings  and  10%,  by  weight,  of  cement,  this  fine  ma¬ 
terial  being  graded  to  an  ellipse. 

Straight  Jerome  Park  material,  21-in.  stone  and  screenings, 
mixed  to  the  best  ideal  curve  with  8,  121  and  15%  cement  to  total 
weight  of  dry  materials. 

Straight  Cowe  Bay  material,  using,  respectively,  2-1-in.,  1-in.  and 
1-in.  gravel,  mixed  with  Cowe  Bay  sand  and  10%  cement,  by  weight, 
and  graded  to  best  ideal  curve  for  each  size;  also,  in  natural  propor¬ 
tions,  1:3:6;  and  also  to  a  curve  identical  with  one  of  the  straight 
Jerome  Park  curves. 

Straight  Cowe  Bay  material,  using  21-in.  and  1-in.  stone  of  uni¬ 
form  size,  mixed  with  Cowe  Bay  sand  and  10%,  by  weight,  and  this 
fine  material  graded  to  an  ellipse. 

Mixed  Jerome  Park  broken  stone  and  Cowe  Bay  sand,  using, 
respectively,  21-in.,  1-in.  and  1-in.  stone,  mixed  with  Cowe  Bay 
sand,  and  10%  cement,  by  weight,  and  graded  to  best  ideal  curve  for 
each  size;  also,  in  natural  proportions,  1:3:6;  and  also  to  a  curve 
identical  with  one  of  the  straight  Jerome  Park  curves. 

Methods  of  Preparing  Materials  for  Natural  Proportions. 

A  few  mixtures  were  made  in  ordinary  proportions,  1 :  21 :  61, 
1:3:6,  and  1 :  31 :  51,  as  scheduled  above,  for  comparison  with  the 
ideal  proportions.  Instead  of  using  for  the  aggregates  the  natural 
materials  as  they  came  from  the  crusher,  which  varied  from  day  to 
day  because  of  the  difference  in  methods  of  handling  and  in  the 
character  of  the  stone  in  different  parts  of  the  ledge,  an  average 
mechanical  analysis  of  the  screenings  as  they  came  from  the  crusher 
was  made  by  averaging  a  number  of  analyses  of  different  lots  of 
| screenings.  Average  analyses  of  Jerome  Park  broken  stone,  of  Cowe 
Bay  gravel,  and  of  Cowe  Bay  sand,  were  similarly  found.  All  of 
(:hese  average  analyses  are  shown  in  Fig.  14,  page  49,  and  in  Tables 
13  and  24,  pages  85  and  86.  The  analyses  of  the  two  materials 
which  were  to  be  used  together  were  plotted  on  a  diagram  and  com- 


48 


bined  in  the  required  proportions  by  the  ordinary  method  of  com¬ 
bining  mechanical  analysis  curves.* 

The  weights  of  the  various  size  particles  for  each  of  the  beams 
which  were  graded  to  so-called  natural  mixtures  were  obtained  from 
these  combined  curves.  This  eliminated  the  variation  in  the  mate¬ 
rials  coming  from  the  crusher  and  from  the  dredge  on  different  days, 
and  gave  truly  average  mixtures. 

Mechanical  Analysis  Curves  Used  in  Beam  Tests. 

All  of  the  mechanical  analyses  of  the  aggregate  and  cement  which 
were  used  in  the  concretes  for  the  1905  beam  tests  are  drawn  to 
scale  in  Figs.  15  to  20,  inclusive.  On  two  of  the  diagrams, 
Figs.  19  and  20,  curves  are  drawn  with  the  lower  portions  as 
parabolas  instead  of  ellipses.  These  represent  trial  mixtures  which 
were  each  used  for  a  single  beam,  but,  giving  unsatisfactory  results, 
were  discarded.  The  combination  of  straight  line  and  ellipse  gives 
a  curve  which  is  really  nearer  a  full  parabola  than  does  the  combina¬ 
tion  of  a  short  parabola  and  straight  line.  When  making  the  density 
tests,  the  analysis  curves  for  obtaining  the  weights  of  the  different 
size  particles,  instead  of  being  drawn  to  a  percentage  scale,  were 
drawn  with  the  top  line  of  the  diagram  representing  the  total 
weight  of  the  aggregate  plus  the  cement.  In  this  way  the  weight 
could  be  read  directly  from  the  curve,  thus  avoiding  the  necessity  of 
changing  the  percentages  to  weights  by  means  of  the  slide  rule. 

It  was  found  by  experiment  that  more  sand  was  required  in  the 
best  ideal  curves  used  in  the  beam  mixtures  than  was  indicated  by 
the  best  ideal  curves  in  the  volumetric  tests  for  density.  With  the 
larger  quantity  of  materials  required  for  the  beams,  the  mixing  could 
not  be  so  thorough,  nor  the  placing  and  compacting  so  careful.  Ac¬ 
cordingly,  the  ideal  curves  in  Fig.  7  are  all  uniformly  higher  than 
would  be  expected  from  the  density  experiments.  In  some  of  the 
diagrams,  a  larger  number  of  curves  were  drawn  than  would  appear 
from  the  schedule  to  be  needed.  This  was  due  to  the  fact  just  men¬ 
tioned.  The  first  mixtures  were  made  with  curves  corresponding  to 
the  best  curves  of  the  density  tests,  and  it  was  found  necessary  to 
raise  all  of  them  about  2%  at  the  tangent  point  to  prevent  a  very 

*Full  description  of  method  of  combining:  mechanical  analysis  curves  are  given  in  a 
chapter  by  Mr.  Fuller  in  Taylor  and  Thompson’s  “Concrete,  Plain  and  Reinforced,”  1905, 
pp.  194  to  209. 


' 


49 


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50 


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51 


Fig.  16.— Mechanical  Analyses  of  Cement,  and  Cowe  Bay  Sand  and  Stone  of  2^-In.  Maximum  Diameter  Used  in  1906  Beam  Tests. 


53 


Fig.  17.— Mechanical  Analyses  op  Cement,  and  Cowe  Bay  Sand  and  Jerome  Park  Stone  of  \  and  1-In.  Maximum  Diameter  Used 


55 


Fig.  19.— Mechanical  Analyses  of  Cement,  and  Jerome  Park  Screenings  and  Stone  of  A  and  1-In.  Maximum  Diameter  Used 

in  1905  Beam  Tests, 


56 


57 


rough  surface  to  the  beam,  which  indicated  that  there  was  not  suffi¬ 
cient  mortar  to  fill  the  voids  in  the  stone.  In  Tables  14  a  to  e,  which 
gives  the  full  data  on  the  beam  tests,  these  specimens  are  desig¬ 
nated  in  the  remarks.  The  results  from  them,  especially  in  the 
density  tests,  cannot  be  considered  absolutely  reliable. 

Equations  of  Mechanical  Analysis  Curves  for  Artificial  Propor¬ 
tioning  of  Aggregates  and  Cement. 

Table  6  gives  in  full  the  equations  of  all  the  curves  of  artificial 
mixes  which  were  used  in  manufacturing  the  beams.  The  curves 
are  numbered  in  Table  6,  and  corresponding  numbers  placed  on 
the  curves  in  the  diagrams,  Fig.  7  (which  contains  all  of  the  ideal 
curves)  and  Figs.  15  to  20. 

Comparative  Tests  Forming  Basis  of  Conclusions. 

Before  giving  the  full  table  (Tables  14  a  to  e)  of  beam  tests,  a 
number  of  short  tables  are  presented,  showing  the  comparative 
strength  and  density  of  the  specimens  which  illustrate  various  laws 
of  proportioning  and  form  the  basis  of  the  conclusions  presented. 

Comparative  Density  and  Strength  of  1 :  9  (by  Weight)  Concrete 
with  Aggregates  of  Different  Maximum  Size. 

In  Table  7  are  tabulated  averages  of  density  and  of  breaking 
|  tests  of  concrete  mixtures  of  cement  and  aggregate  of  different  maxi¬ 
mum  size.  The  figures  represent  averages  of  all  specimens  tested 
according  to  each  character  of  mixing  with  the  exception  of  four 
specimens  omitted,  where  exceptionally  low  strength  is  due  to  voids 
not  being  filled.  In  every  case  but  one  the  mixture  with  2|-in. 
j  stone  for  the  maximum  size  is  denser  than  that  with  1-in.  stone, 

!  and  in  every  case  but  one  the  1-in.  is  denser  than  the  i-in-.  The 

|  modulus  of  rupture  and  the  compressive  strength  of  the  specimens 
with  the  three  sizes  of  stone  follow  the  same  general  order,  the  con¬ 
crete  with  coarse  stone  being  always  stronger  than  the  finer  except 
in  one  case  where  the  1-in.  is  1%  stronger  than  the  2^-in. 

The  general  averages  are  calculated  at  the  bottom  of  the  table, 
and  also  the  ratios  of  density  and  strength  based  on  the  2^-in. 
material  as  unity.  Comparing  these  ratios  with  the  ratios  of  strength 


TxVBLE  7. — Aggregates  of  Different  Maximum  Size.  Comparative  Density  and  Strength. 


58 


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59 


with  different  percentages  of  cement  as  given  in  Table  13,  page  71, 
it  appears  that  an  additional  amount  of  cement  to  the  exent  of  about 
i  part  with  the  maximum  aggregate  1  in.  and  i  part  with  the  maxi¬ 
mum  aggregate  i  inch  will  be  required  to  produce  a  concrete  equal 
in  strength  to  a  concrete  having  a  maximum  aggregate  of  2\  in. 

I  Comparative  Strength  of  1:  9  (by  Weight)  Concrete  with  Jerome 
Park  vs.  Cowe  Bay  vs.  Mixed  Aggregates. 

Tables  8  and  9  give  the  comparative  density  and  strength  of 
concrete  made  with  Jerome  Park  stone  and  screenings  vs.  Cowe  Bay 
gravel  and  sand  vs.  Jerome  Park  stone  and  Cowe  Bay  sand.  The 
!  proportions  are  given  as  1 :  9  and  1:3:6  by  weight.  This  is  not 
|  -  strictly  correct  because  in  order  to  make  a  true  comparison  of  the 
different  materials  a  correction  was  made  for  the  Cowe  Bay  mix¬ 
tures.  Actually,  the  proportions  for  the  straight  Cowe  Bay  are 
\  1:  8.43,  and  1:  2.81:  5.62,  and  the  actual  proportions  by  weight  for 
the  mixed  materials  are  1 :  8.80  and  1 :  2.92 :  5.88.  By  making  this 

•  correction,  the  proportions  by  absolute  volume  are  exactly  the  same, 
1  and  as  it  is  this  which  affects  the  composition,  it  is  the  proper  method 

|  of  proportioning.  The  results,  accordingly,  show  the  true  relation 
between  the  rounded  gravel  and  the  broken  stone. 

The  values  in  Table  8  are  the  results  of  tests  of  concrete  com- 
1  posed  of  the  aggregates  and  10%,  by  weight,  of  cement  graded  to  the 
best  elliptical  curve  for  each  material,  which  represents  in  general 
the  best  possible  mixture  of  each  material  with  the  given  percentage 
I  of  cement.  In  general,  the  straight  Cowe  Bay  material  produces  the 
t  greatest  density.  This  is  undoubtedly  due  to  the  rounded  character 
j  of  the  grains,  and  is  in  accord  with  the  results  of  other  experi- 
.  menters.  The  mixed  Jerome  Park  stone  and  Cowe  Bay  sand  forms 
a  concrete  less  dense  than  the  straight  Cowe  Bay  material  but  denser 
than  the  straight  Jerome  Park;  in  other  words,  it  is  intermediate 
I  between  the  two. 

The  breaking  strength  does  not  follow  the  same  direction  as  the 

•  density.  The  most  noticeable  difference  is  between  the  straight 
Cowe  Bay  and  the  mixed  Jerome  Park  stone  and  Cowe  Bay  sand. 
The  straight  Cowe  Bay  material,  although  producing  a  denser  mix¬ 
ture,  is  not  so  strong  as  the  mixed  material  in  two  cases  out  of 


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Compressive  Strength  at  140 
Days,  Lbs.  per  Sq.  In. 

J.  Park 

stone.  C. 

Bay  sand. 

1  888 

1  770 

1  243 

1  634 

3 

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gravel  and 

sand. 

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stone  and 

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Modulus  of  Rupture  at  90 
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stone.  C. 
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155,  157,  217,  220,  213,  214. . . 

151,  152,  223,  226,  210 . 

164,  165,  259,  211,  212 . 

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61 


three.  An  examination  of  the  tests  indicates  that  the  one  test  with 
i-in.  stone  which  does  not  follow  this  rule  is  the  erratic  one  rather 
than  the  other  two,  since  in  the  transverse  tests  the  difference  in  the 
i-in.  specimens  is  only  2%,  whereas  the  difference  in  the  tests  of 
larger  (2J  in.  and  1  in.)  stone  is  much  greater,  while  in  the  com¬ 
pressive  tests  the  strength  of  the  |-in.  specimens,  which  averages 
1  610  lb.,  appears  abnormally  large,  being,  in  fact,  greater  than  the 
tests  above  it  with  the  coarser  stone.  It  would  appear  from  this  that 
broken  stone  concrete  of  mica  schist  rock  is  stronger  than  gravel 
concrete  under  like  conditions,  and  that  this  increase  in  strength  is 
due  to  the  difference  in  the  surface  of  the  coarse  particles  of  stone. 
This,  in  general,  is  in  accordance  with  the  results  of  the  best  experi¬ 
ments,  notably  those  of  E.  Candlot,  in  France,  although  it  has  been 
disputed  in  many  quarters. 

In  Table  9  the  mixtures  of  the  different  materials  are  in  the 
same  proportions  (corrected  for  different  specific  gravity),  and  not 
those  demanded  by  the  best  analyses  for  each  material.  The  results 
are,  therefore,  not  apt  to  be  so  conclusive  as  those  scheduled  in  Table 
8,  but  it  will  be  seen  that  they  follow  in  general  the  same  direction. 
The  straight  Cowe  Bay  gravel  and  sand  mixture,  while  considerably 
denser  than  the  mixed  Jerome  Park  stone  and  Cowe  Bay  sand,  is 
generally  of  lower  strength  than  the  latter.  Both  tables  indicate  that 
a  mixture  of  Jerome  Park  stone  and  screenings  gives  a  concrete  of 
lower  density  and  lower  strength  than  either  the  straight  Cowe  Bay 
mixtures  of  the  mixed  Jerome  Park  stone  and  Cowe  Bay  sand.  In 
the  1 :  3 :  6  mixtures.  Table  9,  this  might  be  due  in  part  to  the  fact 
that  the  materials  are  not  graded  to  the  proportions  which  are  best 
for  them,  but  this  difference  is  eliminated  in  Table  8.  Further 
tests  are  essential  to  determine  whether  the  principles  just  stated 
I  apply  to  other  classes  of  broken  stone.  The  age  of  the  specimens 
also  tends  to  affect  the  relative  strength,  because  if  the  mixture  is 
!  rich  enough,  as  the  concrete  becomes  older  there  is  more  and  more 
tendency  in  compressive  tests  for  the  stones  to  shear,  so  that  the 
actual  strength  of  the  particles  of  stone  become  more  and  more  a 
function  of  the  strength  of  the  concrete. 


* 


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Note.— Weights  of  Cowe  Bay  material  are  corrected  for  difference  in  specific  gravity,  so  as  to  have  the  same  relative  absolute  volumes  as 
the  Jerome  Park  material. 

*  Only  two  breaks. 


63 


Comparative  Density  and  Strength  of  1 :  9  (by  Weight)  Concrete 
with  Aggregate  Graded  by  Ideal  Mechanical  Analysis 
Curves  vs.  Mixtures  of  Natural  Materials  in  Ordinary 
Proportions. 

Methods  of  determining  the  best  artificial  mixtures  of  sizes  of 
aggregates  (plus  cement)  are  discussed  on  pages  30  to  37,  and  the 
equations  of  the  ideal  mechanical  analysis  curves  are  given  on  page 
35  and  in  Table  6.  Table  10  compares  density  and  strength  of  con¬ 
crete  graded  by  ideal  mechanical  analysis  curves  with  density  and 
strength  of  natural  proportions.  The  tests  of  graded  mixtures  in 
nearly  every  case  are  higher  than  the  natural  proportions.  Greater 
differences  would  have  appeared  if  the  best  ideal  and  best  natural 
proportions  had  been  selected  instead  of  averaging  all  of  them. 

Instead  of  using  the  average  of  all  the  specimens  made  by  artifi¬ 
cial  curves  and  the  natural  proportions,  if  a  selection  had  been  made 
of  the  specimens  proportioned  by  the  best  ideal  analysis  curve  with 
2^-in.  maximum  stone — that  is,  by  the  lowest  artificial  curve  with 
which  the  voids  were  filled,  and  by  the  best  natural  mixtures  with 
the  same  size  stone,  which,  on  the  whole,  were  the  1:3:6  propor¬ 
tions  the  average  values  of  modulus  of  rupture  would  have  been 
241  lb.  per  square  inch  for  the  ideal  and  211  lb.  per  square  inch  for 
the  natural  proportions,  representing  an  increase  in  strength  of  14% 
by  using  the  ideal  mixtures.  The  desirability  of  using  an  artificially 
graded  mixture  is  therefore  dependent  upon  economic  conditions. 
The  relative  saving  in  cement  is  estimated  with  the  aid  of  the  data 
in  Table  13. 


Comparative  Density  and  Strength  of  1:  9  (by  Weight)  Concrete 
with  Aggregates  Graded  by  Ideal  Mechanical  Analysis 
Curves  Having  Graded  Coarse  Aggregate  vs.  Aggregates 
Graded  Similarly  in  the  Sand  Portion,  but  with  Coarse 
Aggregate  of  Uniform  Size. 

Trial  mixtures  of  concrete  made  in  the  laboratory  with  uniform 
coarse  stone  gave  greater  density  than  could  be  obtained  with  uni¬ 
formly  graded  stone.  However,  in  the  former  nearly  50%  of  the 
weight  of  total  aggregate  consisted  of  particles  of  the  coarsest  diam¬ 
eter  of  stone,  and,  in  mixing,  the  concrete  appeared  very  coarse,  so 


TABLE  10. — Aggregates  Graded  by  Ideal  Mechanical  Analysis  Curves  vs.  Mixtures  of  Natural 
Materials  in  Ordinary  Proportions.  Comparative  Density  and  Strength. 


64 


<N 

A.v.  Compressive  Strength 
at  140  Days,  Lbs  per  Sq.  In.+ 

Natural. 

980 

873 

821 

1  355 

1  505 

1  040 

1325 

1  565 

1240 

g 

3 

Ideal. 

1  342 

950 

915 

1  535 

1  425 

1  610* 

1  669 

1  770 

1  125 

1  334 

o 

A.v.  Modulus  of  Rupture 
at  90  Days,  Lbs.  per  Sq.  In.+ 

Natural. 

•pH  H  <3*  OSOiCO  (3*  CO  <3* 

TH  i>  CO  rH 

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Ideal. 

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236 

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Average 

Density.* 

Natural. 

.821 

.798 

.768 

.826 

.844 

.817 

.834 

.818 

.787 

.810 

i> 

Ideal. 

.851 

.810 

.767 

.863 

.845 

.827 

.861 

.820 

.782 

00 

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Maxi¬ 
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144- 146-148 
149-150-155 
156-157-158 

145- 147-151 

152- 159-160 

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165-195-196 

217-220 

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1  ABLE  11.  Aggregates  Graded  by  Ideal  Mechanical  Analysis  Curves  Having  Graded  Coarse 
Aggregate  vs.  Aggregates  Graded  Similarly  in  the  Sand  Portion,  but  with  Coarse 
Aggregate  of  Uniform  Size.  Comparative  Density  and  Strength. 


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66 


that  it  was  considered  doubtful  whether  the  concrete  would  work 
well  in  practice  because  of  the  apparent  tendency  of  the  mortar  to 
run  away  from  the  stones,  and  leave  pockets  of  stone  and  voids. 
Accordingly,  in  this  1905  series  of  experiments  only  a  few  beams 
were  made  with  stone  of  uniform  size  in  order  to  determine  whether 
the  results  were  sufficiently  good  to  warrant  the  continuation  of  this 
line  of  tests  at  a  future  date  if  circumstances  permitted. 

The  results  as  indicated  in  Table  11  show  no  marked  difference 
between  the  specimens  with  graded  coarse  stone  and  those  with  uni¬ 
form  coarse  stone.  The  former  average  slightly  higher  in  strength, 
while  the  latter  have  slightly  greater  density.  This  is  contrary  to 
what  would  be  expected,  since  the  tests  in  general  indicate  that  the 
densest  mixtures  produce  the  strongest  concrete.  The  fact  can  be 
explained  at  the  present  time  only  by  assuming  that  the  uniform 
coarse  stone  does  tend  to  separate,  as  suggested  above,  and  thus  pro¬ 
duces  a  less  homogeneous  concrete.  Further  tests  are  necessary, 
however,  to  determine  whether  this  is  true  or  whether  these  few 
results  are  abnormal.  The  analysis  curves  employed  in  the  mixtures 
of  uniform  stone  are  indicated  in  Figs.  15,  16,  19  and  20.  They 
were  adopted  as  a  result  of  the  volumetric  or  density  tests.  The 
density  tests  indicated  that  a  slightly  better  mixture  would  have 
been  obtained  by  lowering  the  curve  at  the  juncture  of  the  ellipse 
and  the  first  straight  line,  but  since  they  also  indicated  that  this 
style  of  curve  required  more  very  fine  sand  than  a  curve  with  graded 
coarse  stone,  it  was  thought  best  to  adopt  the  curves  shown,  and  then 
use  for  comparison  with  them  the  specimens  with  the  graded  stone, 
whose  analysis  curve  in  the  sand  portion  was  the  same  ellipse. 

Influence  of  the  Analysis  of  the  Coarse  Aggregate  upon  the 
Strength  of  the  Concrete. — One  of  the  most  important  conclusions 
which  may  be  drawn  from  the  comparative  tests  shown  in  Table  11 
is  that  there  is  comparatively  little  difference  in  the  density  and 
strength  of  concrete,  whatever  may  be  the  analysis  of  the  coarse 
aggregate  (meaning  by  the  coarse  aggregate,  all  the  particles  whose 
sizes  are  greater  than  a  diameter  which  is  one-tenth  the  maximum 
diameter  of  the  stone),  provided  this  coarse  aggregate  does  not  con¬ 
tain  a  greater  weight  of  medium  size  particles  than  can  be  repre¬ 
sented  by  a  straight  line.  In  other  words,  the  coarse  aggregate  may 
be  uniformly  graded  above  the  size  corresponding  to  one-tenth  the 


67 


diameter  of  the  coarsest  particles,  or  it  may  contain  an  excess  of 
uniform  size  stone  whose  diameter  is  the  same  as  the  coarsest  diam¬ 
eter  of  the  graded  stone.  Expressed  in  another  way,  the  effect  upon 
the  density  and  the  strength  is  practically  the  same  whether  uniform 
stone  or  uniformly  graded  stone,  or  a  mixture  between  these  two,  is 
used.  However,  tests  should  be  made  on  a  large  scale  with  concrete 
mixed  by  hand  and  by  machine  before  adopting  uniform  stone  in 
regular  construction  work,  in  order  to  prove  conclusively  that  the 
stones  in  the  mixture  of  uniform  stone  do  not  separate  from  the  mor¬ 
tar;  in  other  words,  that  the  concrete  does  not  work  harshly. 

While  the  tests  of  strength  do  not  include  tests  to  determine 
whether  or  not  it  might  be  possible  to  use  an  excess  of  medium  size 
stone  over  and  above  what  would  be  contained  in  a  uniformly  graded 
coarse  aggregate,  the  tests  of  density  indicate  that  when  the  curve 
of  the  coarse  agg’regate  is  raised  above  a  straight  line,  the  density  is 
immediately  decreased,  signifying  that  the  uniformly  graded  coarse 
aggregate  or  an  aggregate  whose  curve  is  below  a  straight  line,  is  the 
t  to  use. 

Effect  of  Fineness  of  Sand  upon  Density  and  Strength. 

The  relative  effect  of  sand  and  stone  upon  the  density  and 
strength  is  evident  from  the  preceding  paragraphs.  The  density  of 

II  •  the  concrete  is  affected  very  much  more  by  the  variation  in  diameter 
of  the  sand  particles  than  of  the  stone  particles,  an  excess  of  fine 
or  medium  sand  decreases  both  the  density  and  strength  of  the  con¬ 
crete.  The  effect  of  the  fineness  of  the  sand,  that  is,  the  pro¬ 
portions  of  the  different  size  grains,  was  carefully  studied  in  the 
volumetric  tests  described  on  pages  30  to  37  inclusive,  and  the  results 
i a  were  confirmed  by  laboratory  and  field  tests. 

Relation  of  Ideal  Curves  of  Different  Size  Stone. 

From  the  preceding  paragraphs  it  is  evident  that  the  equations 
'  1  of  curyes  given  on  page  35  for  aggregate  plus  cement  show  that,  for 
a  given  character  of  aggregate,  a  single  equation  whose  only  variable 
|  is  the  diameter  of  the  particles  of  maximum  size  will  apply  to  aggre- 
j  gates  whose  maximum  diameter  varies  from  \  in.  to  in. 


68 


Effect  ox  Density  and  Strength  of  Concrete  by  Increasing  Per¬ 
centage  of  Sand  and  Decreasing  Stone. 

The  density  experiments  indicated  very  distinctly  that  the  best 
ideal  curve  of  mechanical  analysis  having  been  found,  raising  this 
curve  in  any  portion  of  its  length  decreases  the  density  of  the  mix¬ 
ture.  Accordingly,  to  test  this  point  in  the  beam  tests,  as  shown  in 
the  diagrams,  Figs.  15  to  20,  specimens  were  also  made  with  each 
material  proportioned  according  to  a  curve  which  was  raised  above 
the  best  ideal  at  the  tangent  point  of  the  ellipse  and  straight  line, 
the  lower  portion  of  these  higher  curves  being  still  in  the  form  of  an 
ellipse  with  the  same  horizontal  or  major  axis  but  a  longer  minor 
axis.  More  simply  expressed,  this  is  equivalent  to  increasing  the 
sand  and  decreasing  the  stone.  It  is  evident  from  an  examination 
of  the  full  data  in  Tables  14  a  to  e  that  the  results  of  this  comparison 
were  not  so  conclusive  as  might  be  desired.  This  is  partly  due  to  the 
slight  difference  between  the  various  curves,  to  the  comparatively 
few  tests  made  with  each  curve,  to  the  variation  which  must  be 
expected  in  all  tests  of  concrete,  and  to  the  fact  that  in  some  of  the 
lowest  curves  the  voids  were  not  entirely  filled  and  therefore  the 
results  less  accurate.  With  the  natural  mixtures  the  same  rather 
inconclusive  results  wTere  obtained,  the  proportions  selected  being  so 
nearly  alike  that  the  difference  is  not  marked.  The  general  trend  of 
the  tests,  however,  indicates  that  the  theory  assumed  is  correct,  and 
it  is  certainly  substantiated  by  previous  tests  made  by  Mr.  Fuller, 
which  indicate  quite  conclusively  that  with  the  same  proportions  of 
cement  to  total  aggregate,  the  strongest  mixture  is  that  with  the 
largest  possible  proportion  of  stone  and  the  smallest  possible  propor¬ 
tion  of  sand. 


TABLE  12.— Effect  on  Density  and  Strength  of  1 :  8  (by  Weight) 
Concrete  of  Increasing  Percentage  of  Sand  and  De¬ 
creasing  Stone.  (From  Little  Falls  Experiments.) 


Proportion  by  W eight  of  Cement 
to  Total  Aggregate. 

Absolute 
Volume 
of  Cement. 

Density,  i.  e.  Total  Av.  Modulus  of 
Cement  Rupture  at  33  Days, 

Sand  +  Stone.  .  Lbs.  per  Sq.  In. 

1:8 

1:2:8 

.091 

.865 

319 

1:8 

1:3:5 

.086 

.833 

285 

1:8 

1:4:4 

.082 

.801 

209 

1:8 

1:5:3 

.080 

.799 

151 

1:8 

1:6:2 

.076 

.760 

102 

1:8 

1:8:0 

.073 

.754 

41 

69 


In  Table  12  are  given  the  results  selected  from  tests  at  Little 
I  Tails,  N.  J.,  made  in  1901.  All  of  the  specimens  presented  have  the 
i  same  proportions  by  weight,  namely  1 :  8.  The  ratio  of  sand  to  stone, 
however,  is  varied  from  2 :  6  to  8 :  0.  It  is  seen  from  an  inspection  of 
the  table  that  in  every  case  there  is  an  increase  in  both  density  and 
strength  as  stone  is  substituted  for  an  equal  weight  of  sand. 

Proportioning  Sand  and  Stone  in  Practice. 

Where  two  aggregates  are  used,  such  as  natural  sand  and  natural 
gravel,  or  crusher-run  screenings  and  crusher-run  broken  stone,  it 
is  evident  from  the  preceding  paragraphs  that  the  relative  propor¬ 
tions  of  sand  to  stone  may  be  properly  graded  in  the  field  from  day 
to  day  by  employing  in  all  cases  as  little  sand  as  may  be  and  avoid 
visible  voids  in  the  concrete.  In  practice,  when  proportioned  in 
this  way  the  mixture  is  found  to  be  not  only  theoretically  denser 
and  stronger,  but  it  works  most  smoothly  in  placing.  Accordingly, 
in  laying  the  lining  in  Jerome  Park  Reservoir,  the  inspectors  were 
instructed  to  vary  slightly  from  day  to  day  the  relative  proportions 
of  sand  to  stone,  according  to  the  way  the  material  was  running 
as  it  comes  from  'die  crusher,  or  the  bank,  while  using  at  all  times 
the  same  total  volu  me  of  total  aggregate.  Having  selected  a  ratio  of 
cement  to  total  aggregate,  this  gives  a  better  and  easier  method  of 
proportioning  in  ci.ses  where  it  is  not  considered  economical  to  use 
more  than  two  aggregates — that  is,  where  artificial  grading  is  pro¬ 
hibited— than  any  number  of  theoretical  tests.  This  plan  is  also 
especially  advantageous  where  the  sand  varies  in  fineness  from  day 
to  day,  for  the  finer  the  sand,  the  farther  it  will  spread,  and  the  less 
of  it  is  required  to  fill  the  voids  of  the  stone,  and  also  the  less  of  it 
should  be  used  in  proportion  to  the  cement,  since  a  mortar  of  fine 
sand  is  weaker  than  a  mortar  of  coarse  sand. 

Comparative  Density  and  Strength  of  Similar  Concrete  with 
Different  Percentages  of  Cement  and  21-inch  Stone  Graded 
as  an  Ellipse  and  Straight  Line. 

In  Table  13  is  tabulated  the  density  and  strength  of  beams  in 
which  different  percentages  of  cement  are  used  to  the  weight  of  the 
total  dry  material,  ranging  in  percentages  from  8  to  15-  per  cent,  and 


70 


in  proportions  by  weight  from  1 :  11.5  to  1 :  5.7,  thus  covering  all 
ordinary  proportions  in  practice.  As  the  percentage  of  cement  is 
increased,  the  strength  increases  and  in  nearly  similar  ratios. 

Effect  upon  Density  of  Substituting  Cement  for  Fine  Sand. 

The  average  densities  in  Table  13  show  an  extreme  variation  of 
less  than  1  per  cent.  This  is  in  confirmation  of  the  statement  already 
made  that  a  substitution  of  cement  for  fine  sand  having  grains  of 
the  same  diameter  does  not  affect  the  density.  This  is  also  proved 
still  more  definitely  in  the  volumetric  tests  of  density.  As  the 
mechanical  analysis  curves  in  all  the  beam  mixtures  include  both 
cement  and  aggregate,  in  the  specimens  with  different  percentages  of 
cement  the  additional  cement  is  actually  substituted  for  sand  hav¬ 
ing  the  same  size  grains. 

Complete  Schedule  of  Transverse  and  Compressive  Tests,  1905. 

In  Tables  14a-e  are  given  the  complete  results  of  the  tests  of 
concrete  beams  together  with  the  reports  of  the  compressive  strength 
of  the  pieces  of  beam  which  were  capped  with  neat  cement. 

Nearly  all  the  tests  given  in  these  tables  have  already  been  in¬ 
cluded  in  the  short  comparative  tables,  and  most  of  the  results  of 
apparent  value  have  been  presented  there.  Because  of  the  difference- 
in  age  of  the  transverse  and  compressive  tests,  no  decisive  ratio  can. 
be  calculated  between  the  transverse  moduli  of  rupture  and  the  com¬ 
pressive  strengths  of  the  same  specimens.  The  age  is  somewhat  diffi¬ 
cult  to  allow  for,  as  the  growth  of  strength  in  tension  and  compres¬ 
sion  are  not  necessarily  in  the  same  ratio.  Most  of  the  beams  are 
in  duplicate,  as  indicated  by  the  bracket  before  the  average  modulus 
of  ruture.  As  a  rule,  the  columns  are  self-explanatory.  Columns  7, 
8  and  9  define  the  mechanical  analysis  curves  where  artificial  mix¬ 
tures  are  employed.  The  analysis  curves  are  all  drawn  in  the  dia¬ 
grams,  Figs.  15  to  20.  As  has  already  been  stated,  a  few  of  the 
curves  have  a  parabola  for  their  beginning,  but  this  was  discarded 
as  giving  less  satisfactory  results  than  the  ellipse.  The  special 
ellipses  used  in  beams  No.  149  and  150  were  discarded  because  there 
was  not  sufficient  fine  material  to  fill  the  voids.  All  of  the  other 
ellipses  are  drawn  according  to  the  regular  plan  adopted  at  the  out¬ 
set  of  the  experiments. 


TABLE  13. — Comparative  Density  and  Strength  of  Similar  Concrete  with  Different  Percentages  of 
Cement  and  2i-lNCH  Stone  Graded  as  an  Ellipse  and  Straight  Line. 


71 


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The  weights  in  pounds,  Columns  10  to  14,  are  calculated  directly 
from  the  beam  mixing  data.  The  total  weights  per  cubic  foot  of  the 
different  specimens  follow  the  same  general  relation  as  the  densities 
already  referred  to,  the  aggregate  having  coarsest  stone  giving  the 
heaviest  concrete,  and  the  ideal  mixes  being  usually  heavier  than 
the  mixes  of  natural  proportions.  The  Cowe  Bay  materials  give  a 
slightly  lighter  concrete  than  the  Jerome  Park  mixtures  because  of 
their  lighter  specific  gravity,  even  although  they  are  denser.  The 
weights  of  the  concrete  as  mixed  run  from  146  to  162  pounds  per 
cubic  foot. 

Column  15,  as  stated  in  the  foot-note,  represents  the  minimum 
theoretical  weight  of  the  concrete,  assuming  that  this  is  made  up  of 
the  dry  materials  plus  a  quantity  of  water  for  chemical  combination 
equal  to  10%  of  the  weight  of  the  cement.  This  theoretical  mini¬ 
mum  is  from  8  to  12  lb.  below  the  actual  weight  as  mixed. 

Column  16  gives  the  theoretical  weight,  assuming  that  the  voids 
are  all  filled  with  water,  and  a  comparison  of  this  column  with 
column  14  and  also  an  inspection  of  column  21  indicates  that  the 
air  voids  in  most  of  the  mixtures  are  inappreciable,  the  difference 
being  nearly  within  the  limits  of  error  which  must  be  allowed  for  in 
the  weights  and  measurements. 

The  calculated  volumes  of  material  in  one  cubic  foot  of  beam, 
columns  17  to  21,  are  really  absolute  volumes,  the  total  dry  volume, 
column  19,  representing  the  sum  of  the  ratios  of  the  elementary 
volumes  of  the  cement  and  of  the  aggregate  to  the  unit  volume, 
thus  giving  the  density  of  the  mixture. 

Inspection  of  the  quantity  of  water  in  the  beams,  columns  13  and 
20,  reveals  that  the  smaller  stone,  that  is,  the  i-in.,  requires  the  most 
water  in  gaging,  and  the  coarsest  stone,  the  2^-in.  the  least.  The 
Cowe  Bay  gravel  and  sand  require  less  water  than  the  broken  stone 
and  screenings. 

The  total  volume  of  voids  per  cubic  foot,  column  24,  gives 
merely  the  complements  of  the  densities  in  column  19.  The  voids  in 
the  cement,  column  22,  are  based  upon  the  voids  in  the  two  neat 
beams  given  first  in  the  table,  it  being  assumed  in  the  concrete  speci¬ 
mens  that  the  voids  due  to  the  cement  are  in  the  same  ratio  to  the 
weight  of  the  cement  per  cubic  foot  of  concrete  as  the  voids  in  an 
average  neat  beam  are  to  the  weight  of  cement  in  this  neat  beam. 


TABLP  with  Different  Percentages 
ms.  Spans,  68  and  32 


Compressive  Strength  of 
Concrete  Prisms,  6x6 
X  18  Inches.  Average 
Age,  140  Days. 


1  1 

25 

|  26 

|  27 

»  1 

—\ 

29 

30 

1  1 

2 

1  3 

i  4 

\  5 

6 

Modulus  of  Rupture. 

w 

Compressive  Strength. 

£> 

S 

ai 

M 

Pounds 

per  square  inch. 

pd 

© 

rQ 

g 

Pounds 

per  square  inch. 

P 

s 

AS 

S3 

8 

ce 

ra 

5 

a 

| 

© 

tuo 

1 

® 

® 

© 

© 

% 

i 

& 

a 

a 

© 

§ 

© 

=4-4 

4) 

P3 

© 

be 

<1 

o 

o' 

fc 

a 

1 

| 

'3 

§ 

e3 

© 

► 

<1 

Ph 

© 

® 

tf-. 

® 

« 

<4-1 

o 

o’ 

0 

a 

M 

ce 

§ 

3 

a 

a 

g 

tuo 

c3 

c 

© 

> 

219 

201 

2(2 

90 

3 

295 

276 

285 

219 

135 

141 

142 
139 

2 

2 

2 

2 

1  775 
1  375 
1  565 
1  875 

1  410 
1  265 
1  550 

1  590 
1  320 
1  560 
1  770 

91 

91 

90 

3 

3 

3 

248 

290 

300 

220 

246 

280 

J-251 

288 

Surface  rocky. 

201 

202 

210 

210 

1  ooU 

203 

90 

qa 

3 

O 

298 

OQ  Q 

234 

OKK 

J-276 

203 

141 

2 

1  745 

1  555 

1  650 

204 

Ol  K 

91 

/C 

3 

/Cvo 

261 

4DD 

241 

249 

204 

215 

141 

136 

2 

2 

1  520 

1  435 
1  345 

1  475 
1  445 

/ClD 

211 

90 
q  a 

1 

9 

196 

196 

ono 

1-205 

211 

139 

2 

1  175 

1  085 

1  130 

212 

207 

«7U 

91 

O 

3 

Q 

<C\  ( 
222 
OQK 

iCUC 

210 

1 

[-212 

212 

207 

139 

140 

2 

2 

1  170 
1  385 

1  080 
1  235 

1  125 
1  310 

208 

yi 

O 

/Coo 

lu/C 

I 

208 

140 

2 

1  205 

1  145 

1  175 

218 
oi  a 

90 

91 

3 

3 

413 

445 

353 

391 

379 

409 

Slightly  rocky. 

218 

216 

135 

136 

2 

2 

2  230 

2  150 
1  840 

2  190 
2  140 

<410 

/C  e±Q\) 

gravel, 
1.00;  Je 
Neat,  7 


gs  and  stone  varies  with  mixture;  Cowe  Bay  sand  (natural)  1  11-  Pnwp 
md,  2.65;  Cowe  Bay  gravel  2.65  Weights  per  cubic  ^oo^as  miied  clment 
Cowe  Bay  gravel,  102.7.  Tensile  strength  cement,  pounds  per  square  mch  - 


16  represents  theoretical  maximum,  assuming  voids  filled  with  water. 


TABLE  14  e.— Composition  and  Transvebse  Strength  of  Concrete  Beams  Made  with  Different  Aggregates  of  Various  Analyses  Mixed  with  Different  Percentages  Compressive  Strength  of 
of  Cement,  Tested  at  Jerome  Park  Reservoir  by  the  Aqueduct  Commission  during  the  Year  1905.  Beams,  6  x  6  X  72  Inches.  Spans.  68  and  32  Concrete  Prisms,  6x6 

Inches.  Giant  Portland  Cement.  Age,  90  Days.  *  Avebaoe 

Age,  140  Days. 


2 

3 

4 

5 

6 

7 

8 

9 

10 

12 

13 

14 

15 

1  16 

17 

18 

1  19 

20  |  21 

22  |  23  24 

25 

26 

,  27 

28 

29 

30 

1 

2 

8 

4  1 

5 

6 

Cement  to  total  dry 
materials,  )£. 

Kind  of  stone. 

Kind  of  sand. 

I  Maximum  size  of 

stone. 

Uniformly  graded 
above  diameter, 

inches. 

1  Per  cent,  finer  than 

diameter  in  Col.  7.* 

Curve  below 

diameter  in  Col.  7,t 

Weight  in  Lbs.  of  Materials  in  1 
Ft.  of  Beam  as  Mixed. 

Cu. 

Calculated  Volume  in 
Cubic  Feet  of 
Material  in  1  Cu.  Ft. 
of  Beam  as  Mixed. 

Volume  of 
Voids  in 

1  Cu.  Ft. 

Modulus  of  Rupture. 

00 

§ 

1 

£ 

Reference  numbers.  | 

COHPRI 

lssive  Strength. 

Pounds 

per  square  inch. 

Proportions  by 
weight. 

[  Age,  days.  1 

|  No.  of  breaks.  1 

Pounds 

per  square  inch. 

l 

8 

|  Aggregate. 

1  Total 

dry  mix. 

s 

03 

£ 

Totals. 

Age. 

! 

s 

|  Minimum. 

|  Maximum. 

|  Cement. 

Aggregate. 

|  Total  dry. 

|  Water. 

Total. 

a 

8 

Aggregate. 

3 

a 

i 

1 

a 

1  Minimum. 

Average. 

l 

6 

Z 

Maximum. 

Minimum,  i 

1 

Average,  i 

10.2 

J.  Park. 

Cowe  Bay. 

0  20 

37.8 

Ellipse. 

15.0 

132.0 

147.0 

10.0 

167.0 

148.2 

156.4 

.078 

.772 

.850 

— 

.160  1.010 

066 

.084 

.150 

90 

3 

295 

276 

1  1 

* 

— 

1:8*° 

10.2 

o5o 

3i.2 

14.5 

128.0 

142.6 

11.6 

154.1 

143.7 

153.6 

.075 

.748 

.823 

.ISO  ]  ill  III 

i064 

.113 

.177 

91 

:: 

248 

220 

)  net 

1  775; 

1  410 

1  590 

1:880 

10.2 

0.10 

SI. 2 

14.5 

127.8 

142.3 

10.8 

153.1 

143.5 

153.6 

.075 

.745 

.820 

•  173  . 99:; 

.064 

.116 

.180 

91 

3 

290 

246 

>251 

Surface  rocky. 

1  265 

1  320 

1:8*° 

10.2 

1  " 

0.10 

33.2 

14.5 

127.6 

142.1 

10.3 

152.4 

143.3 

153.3 

.075 

.745 

.820 

.163  .983 

.064 

.116 

.180 

90 

3 

800 

280 

288 

210 

139 

2 

1  666 
l  875 

1  660 

1  770 

1:2":688 

10.2 

« 

1  " 

14.5 

127.5 

142  0 

9.7 

151.7 

143.2 

153.2 

.075 

.745 

820 

.156  .976 

.064 

.116 

.180 

90 

3 

298 

234 

i 

208 

141 

1  7451 

r 

1:293:588 

10.2 

14.4 

126.7 

141.1 

9.8 

150.9 

142.3 

152.6 

.075 

.740 

!815 

.1.-.;  .'.>72 

.064 

.121 

.185 

90 

2 

298 

255 

204 

141 

1:880 

10.2 

1  " 

"56' 

'37\7* 

Ellipse. 

14.4 

126.7 

141.1 

11.0 

152. lj 

142.3 

152.6 

.075 

.740 

.815 

.176  .991 

.064 

.121 

.185 

91 

3 

261 

241 

249 

215 

136 

2 

1  545 

1  345 

1  445 

1:880 

10.2 

h" 

.075 

34.4 

13.9 

122.3 

136.2 

12.8 

149.0 

137.3 

149.6 

.072 

.715 

.78? 

.205  .992 

.061 

.152 

.213 

90 

1 

196 

196 

i 

211 

139 

1:880 

10.2 

j" 

.075 

34.4 

13.7 

120,4 

134.1 

14.9 

149.0, 

135.2 

148.1 

.071 

.705 

.776 

.239  1.015 

.060 

.164 

90 

3 

817 

202 

r  205 

1  180 

1:2W3:588 

10.2 

f 

13.8 

121.3 

134.1 

12.4 

147.5 

135.2 

147.6 

.073 

.710 

.7(-3 

.199  .982 

.062 

.155 

i217 

91 

3 

838 

210 

(.910 

207 

140 

2 

1  885 

1  080 
1  285 

1  310 

1:2":588 

10.2 

14.0 

123.0 

137.0 

12.8 

149.31 

138.1 

150.0 

.072 

.719 

.791 

.197  .988 

.061 

.148 

.209 

91 

3 

235 

192 

208 

140 

2 

1  205 

1  115 

1  175 

1:687 

12| 

21" 

0.20 

33.8 

Ellipse. 

19.2 

131.3 

150.5 

9.4 

159.9 

152.0 

158.9 

.099 

.767 

.SI  Hi 

.151  1.017 

.084 

.050 

.134 

90 

3 

418 

853 

879 

Slightly  rocky. 

218 

185 

2 

2  230 

2  150 

1:6®* 

15.3 

H" 

0.20 

33.8 

22.7 

126.0 

148.7 

9.6 

158. 8j 

150.5 

157.9 

|.117 

.735 

.154 |  1.006 

.099 

.049 

.148 

91 

3 

445 

891 

409 

216 

180 

2 

2  440 

1  840 

2  140 

Note  —  Volumes,  cubic  feet  per  100  lbs.  as  mixed  :  Cement,  1.00;  Jerome  Park  screenings  (Crusher  Rimi,  1.06;  Jerome  Park  stone,  1.03:  mixture  Jerome  Park  screenings  and  stone  varies  with  mixture;  Cowe  Bay  sand  (natural)  in  -  „ 

■Travel  0  '17  Specific  gravity:  Cement,  8.10;  Jerome  Park  screenings  varies  with  size;  Jerome  Park  stone,  2.78;  mixture  Jerome  Park  screenings  and  stone,  2.77:  Cowe  Bay  sand,  2.65;  Cowe  Bay  gravel,  2.65.  Weights  per  cubic  foot  iN  nnmi  r'l'  •' 
l  on-  Jerome  Park  screenings  (Crusher  Run),  94.8;  Jerome  Park  stone,  9.70;  mixture  Jerome  Park  screenings  and  stone  varies  with  mixture;  Cowe  Bay  sand  (natural),  0.90;  Cowe  Bay  gravel,  102.7.  Tensile  strength  cement  pounds  ner  so  iar«  imli  ' 
Neat  7  days,  662;  28  days,  695;  8  months,  720.  F  H  men. 

’  ( lol  15  =  Col.  10  X  0.08  4-  Col.  12.  Col.  16  =  Col.  12  +  (Col.  24  X  62.4).  Col.  15  represents  theoretical  minimum,  assuming  &X  of  water  for  chemical  combination.  Col.  16  repx-esents  theoretical  maximum,  assuming  voids  filled  with  wntu,- 
*  Including  cement.  r  See  separate  table  for  equations.  • 


TABLE  15.  -  Composition  and  Transverse  Strength  of  Beams  of  Neat  Cement  and  1:9  (by 
and  Jerome  Park  Screenings  and  2J-Inch  Stone.  Beams  6  X  6  X  72  Inches. 


Weight)  Concrete  Made  with  Various  Brands  of  Cement 
Spans,  68  and  30  Inches.  Age,  90  Days. 


Compressive  Strength 
of  Concrete  Prisms, 
6  X  6  x  18  Inches 
Average  Age,  140 
Days. 


Reference  numbers.  ~ 

2 

3 

4 

6 

6 

7 

8 

9 

10 

n 

42 

1  18 

|  14 

1  15 

16 

17 

18 

19 

20 

1  21 

22 

|  23 

|  24 

25 

26 

27 

|  28 

29 

1  1 

2 

1  3 

1  4 

1  6 

1  8 

Brand  of  Cement. 

Proportions  by 
weight. 

Kind  of  stone. 

Kind  of  sand. 

Maximum  size  of 
stone. 

]  Uniformly  graded 

above  diameter, 
inches. 

Per  cent,  finer  than 
diameter  in  Col.  7. 

Curve  below 
diameter  in  Col.  7. 

Weight  in  Lbs.  of  Materials  in  1 
Ft.  of  Beam  as  Mixed. 

:cu. 

Calculated  Volume  in 
Cubic  Feet  of 
Materials  in  1  Cu.  Ft. 
of  Beam  as  Mixed. 

Volume  op 
Voids  in 

1  Cu.  Ft. 

Modulus  of  Rupture. 

Reference  numbers. 

Compressive  Strength. 

Age,  days. 

No.  of  breaks. 

Pound 
per  square 

s 

inch. 

6 

< 

No.  of  breaks. 

Pounds 

per  square  inch. 

Cement. 

Aggregate. 

Total 

dry  mixed. 

Water. 

Totals. 

•g 

a 

•«! 

Minimum. 

Maximum,  j 

Cement.  1 

Aggregate.  | 

Total  dry. 

Water. 

|  Total. 

Cement.  I 

Aggregate. 

Total. 

Maximum. 

Minimum, 

1  £ 

■5 

Maximum.  1 

I 

a 

1 

a 

Average. 

210 

Giant 

Neat  Cement. 

104.5 

104.5 

29.6 

134.1 

112.9 

133.1 

.541 

.541 

.475 

1.016 

.459 

.... 

.459 

89 

3 

1  177 

929 

l01(1 

210 

100.5 

100.5 

30.4 

130.9 

108.5 

180. 4;.  530 

•••• 

.520 

.487 

1.007 

.480 

"" 

.480 

91 

3 

70S 

744 

199 

103.4 

103.4 

29.7 

133.1 

111.7 

132.4  .535 

.535 

.485 

1.020 

.465 

.465 

91 

3 

591* 

260 

888 

Atlas 

101.0 

101.0 

28.5 

129.5 

109.1 

129.  1 

.560 

.550 

.450 

1.060 

.450 

.450 

91 

3 

852 

827 

880 

238. 

280 

Universal 

100.8 

100.8 

30.9 

131.7 

108.9 

129.4 

.541 

.541 

.495 

1.036 

.459 

.459 

91 

8 

766 

717 

748 

239 

210 

Empire 

101.9 

101.9 

31.2 

133.1 

110.0 

131.2 

.530 

.530 

.482 

1.012 

.470 

.470 

91 

3 

1  087 

955 

1  028 

240 

211 

Iron  Clad 

96.0 

96.0 

2s.  9 

124.9 

103.7 

126.6' 

.510 

.510 

.463 

.973 

.490 

.490 

90 

662 

598 

241 

Hudson  River 

101.2 

101.2 

31.2 

132.4 

109.3 

130.1 

.537 

.537 

.600 

1.037 

.463 

.463 

90 

3 

608 

613 

632 

242 

Pennsylvania 

97  3 

97.3 

27.8 

125.1 

105.1 

127  9 

.510 

.510 

.445 

.955 

.490 

.190 

90 

3 

790 

703 

737 

243 

\\  Vlltt'lot  t  e 

91  9 

91  9 

31.0 

122.9 

99  3 

133  '.1 

.488 

.488 

495 

.983 

.512 

.... 

.512 

90 

3 

774 

509 

244 

215 

Atlas 

1:9 

J.  Park. 

J.  Park. 

0.20 

37.8 

Ellipse. 

14.7 

132.0 

146.7 

10.7 

157.4 

147.91 

156.71.078 

.762 

.840 

.171 

1.011 

.004 

|:096 

.160 

88 

191 

191 

| 

315 

187 

2 

1  295 

1  285 

1  290 

216 

14.2 

128.0 

142.2 

12.0 

154.2 

143.3, 

153.7,  .076 

.740 

.816 

.193 

1.009 

.062  .122 

.184 

88 

2 

858 

192 

I 

246 

137 

2 

1  806 

1  160 

1  260 

247 

Universal 

14.2 

127.9 

142.1 

12.0 

154.1 

148.2 

153.1 

.076 

.748 

.824 

.192 

1.016 

.064  .112 

.170 

88 

2 

190 

156 

| 

247 

136 

2 

1  140 

960 

1  060 

248 

14.3 

188.7 

143.0 

11.8 

154.8 

144.1 

154. 2  .077 

.744 

.821 

.189 

1.010 

.065 

i.114 

.179 

93 

1 

160 

160  , 

248 

135 

2 

1  060 

885 

976 

219 

Empire 

14.3 

128.3 

142.6 

11.4 

154.0 

143.7 

154.0 

.075 

.743 

.818 

.183 

1.001 

.067 

.n.j 

.182 

93 

3 

195  1 

249 

185 

3 

1  050 

910 

980 

250 

“ 

14.3 

128.8 

143.1 

11.9 

155,0 

144.2 

1544 

.075 

.744 

.819 

.190 

1.009 

.067 

,m 

.181 

93 

3 

232 

f230 

250 

185 

2 

1  3110 

995 

1  125 

851 

Ironclad 

14.3 

127.3 

141.6 

11.9 

153.5 

142.7 

153.4 

.076 

.735 

.811 

.191 

1.002 

.073  .116 

.189 

91 

3 

228 

187 

1 

251 

133 

2 

1  145 

890 

1  020 

252 

14.2 

142.2 

11.8 

154. 0 

143.3 

1  153.7; 

.075 

.740 

.815 

1.004 

.072  .113 

.185 

91 

350 

186 

353 

133 

2 

1  075 

890 

980 

268 

Hudson  River 

14.3 

128> 

11.9 

154.9 

144.1 

|  154. 31 

.075 

.743 

.818 

>91 

1.0091.065 

.117 

.182 

92 

2 

213 

194 

1 917 ! 

253 

134 

2 

1  150 

1  070 

1  110 

254 

14.3 

128.5 

142.8 

12.2 

156.0 

143.9 

!  154.2 

.075 

.742 

.817 

.195 

1.012  .065 

.118 

.183 

92 

1 

214 

214 

,217 

254 

134  2 

1  135 

1  080 

1  110 

255 

Pennsylvania 

14.1 

127.0 

141.1 

11.6 

152.7 

142.2 

153.1 

.074 

.733 

.807 

.186 

.993  .  071 

.122 

.193 

91 

3 

224 

224 

, 

255 

133 

2 

1  390 

1  340 

1  365 

14.4 

129.7 

144.1 

11.8 

155.0 

145.3 

155.1 1 

.075 

.748 

.189 

1.012 

.072  .105 

.177 

91 

3 

215 

215  | 

256 

133 

2 

1  500 

1  400 

1  450 

951 

Wyandotte 

14.5 

130.4 

144.9 

11.6 

156.5 

146.1 

155. 4'.  077 

.753 

!830 

.186 

1.016 

.091 

.079 

.170 

91 

3 

230 

230  | 

257 

133 

2 

1  :*45 

1  206 

1  276 

258 

14.6 

130.9 

145.5 

11.8 

157.3 

146.7 

156.0 

.078 

.754 

.832 

.189 

1.021 

1 .082 

j  .086 

.168 

91 

3 

205 

205  | 

' 

258 

133 

2 

1  335 

1  220 

1  225 

Notk. -Specific  Gravity:  Giant,  3.10:  Atlas,  3.02;  Universal,  2.98;  Empire,  3.08;  Ironclad,  3.00;  Hudson  River,  3.04;  Pennsylvania,  3.06;  Wyandotte,  3.02. 

Col.  15  —  Col.  (10  x  0.08)  -4- Col.  12.  Col.  16  =  Col.  12  4-  (Col.  24  x  62.4).  Col.  16  represents  theoretical  minimum,  assuming:  8^  of  water  for  chemical  combination.  Col.  16  represents  theoretical  maximum,  assuming  voids  filled  with 
water.  Aggregate  in  above  table  is  similar  to  that  described  in  previous  table. 

*  Not  included  in  average  because  the  fractured  surfaces  snow  many  air  holes  and  lumps  of  cement. 


TABT/IXED  with  Different 
6  X  6  X  72 


(  Compressive  Strength 
Concrete  Prisms,  6x6 
X  18  Inches.  Average 
Age,  140  Days. 


27 


28  |  29 


ulus  of  Rupture. 


178 

179 

180 

181 

182 

191 

183 

184 

185 

186 

190 

193 

197 

189 

217 
220 
221 
222  ! 


Pounds 

per  square  inch. 


268!  208 
2931  135  / 
235!  223  f  1 


245 


223-} 


334 

292 

289 


Surface  rocky 


I  j  j 

188|‘!  272 ) 
262  |  276 


361  281  I 
346  [  301  f 
331 !  300  / 
305  270  f 

374!  365 

221 i  188 

186  158 
223  139 


1:2 

1:2 


250 

244 

243 

265 


238  f 
176  f 
211  j 
228"/ 


274!  228 


329 -j 
302  -[ 


369 

204 

171 

184 

230  -j 
242-' 


Slightly  rocky 


Surface  rocky 


Slightly  rocky. 


178 

179 

180 

181 

182 

191 

183 

184 

185 

186 

190 

193 

197 


217 

220 

221 

222 

234 

ooo 


© 

5b 

< 

No.  of  breaks. 

Pounds 

per  square  inch. 

Maximum. 

S' 

s 

Average.  1 

| 

1  2 

| 

1  410  1  250 

1  330 

j  1 

1  710  1  710, 

1  710 

2 

1  180|  1  090, 

1  135 

2 

1  495 

i|  1  410 

1  455 

2 

1  440 |  1  315; 

1  375 

2 

1  o65 

i  1  450, 

1  505 

2 

1  920 

1  1  745 

1  830 

2 

1  715 

1  605; 

1  660 

2 

1  795 

1  1  750 

1  770 

! 

2 

1  370  1  630 

1  500 

1 

2 

1  425  1  395 

1  410 

2 

1  100 

940: 

1  020 

•  •  ■  •  J 

2 

965 

915 

940 

2 

970 

970 

970 

•••■ 

2 

1  880 

1  555 

1  715 

2 

1  140 

1  260 

1  350 

....  1 

2 

1  455 

1  175 

1  315 

•••• 

2 

1  485 

1  310 

1  395 

■  J 

2 

1  800 

1  800 

1  800 

11 

1  A  AZ.  1 

■*  t  At:  1 

TABLE  14  c.—  Composition  and  Transverse  Strength  of  Concrete  Beams  Made  with  Different  Aggregates  of  Various  Analyses  Mixed  with  Different 
Percentages  of  Cement  Tested  at  Jerome  Park  Reservoir  by  the  Aqueduct  Commission  during  the  Year  1905.  Beams,  6  X  6  X  72 
Inches.  Spans,  68  and  32  Inches.  Giant  Portland  Cement.  Age,  90  Days. 


(  '(impressive  Strength 
Concrete  Prisms,  6x6 
X  18  Inches.  Average 
Age,  140  Days. 


7 

8 

9 

10 

i' 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21  1 

Uniformly  graded 

above  diameter, 

inches. 

!  Per  cent,  finer  than 

diameter  in  Col.  7* 

Curve  below 

diameter  in  Col.  7.1 

Weight  in  Lbs.  of  Material  in  1  Cu. 

Ft.  of  Beam  as  Mixed. 

Calculated  Volume  in 
Cubic  Feet  of  | 

Material  in  1  Cu.  Ft. 
of  Beam  as  Mixed. 

J  Cement. 

Total 

dry  mix. 

Water. 

Totals. 

As  mixed. 

Minimum. 

Maximum. 

Cement. 

Aggregate. 

Total  dry. 

1 

Total. 

0.20 

85.8 

F.llipse. 

18.5 

129. 6i 

148.1 

9.1 

157.2 

i  140.6* 

157.8 

.096 

.748! 

-11 

.146 

.990 

0.20 

37 .  8 

18.7 

130.8 

140.5 

11.8 

161.3 

;  i5i.o 

158.7 

.097] 

.7551 

.852| 

.189 

1.0411 

0.20 

37 .  8 

18.1 

127.5 

145.6 

11.3 

156.9 

147.0 

156.1 

.094 

.7371 

.831 

.161 

1.IH2 

0.20 

39.4 

18.4  1 

1  128.8 

147.2 

9.7 

156.9 

148.7 

157.8 

.095 

.7481.838 

.155 

998 

0.20 

18.1 

127.0 

145.1 

10.8 

■ 

1  146.5 

155.8 

.094 

.785 

.829 

.173 

1.002 

0.20 

41.3 

17.5 

122.8 

14D.:: 

ll  2 

151.5 

1  141.7 

152.8 

.091 

.709  .800 

.180 

980 

0.20 

37.8 

21.8 

123  6 

145.4 

11.6 

157.0 

147.1 

155.1 

.130 

.718  .8-15 

186 

|  1.031 

0.20 

37.8 

125.0 

147.0 

10.9 

157.9 

148.8 

155.6 

.139 

.722 

.861 

.175 

1  .036 

0.20 

-I  8 

123.4 

145.2 

11.3 

156.5 

146.9 

156.1 

.113 

.713 

.826 

.181 

1  1.007 

0.29  1 

39.4  , 

21.7 

122  ■ 1 

144.6 

11.4 

156.0 

146.3 

155.0 

.124 

.710 

.884 

.188 

j  1.017 

0.20 

41.8 

21.8 

126.5 

148.3 

11.5 

159.8 

150.0 

156.0 

.116 

.7H() 

.876 

.184 

1.060 

0.20  ! 

37.8 

11.6 

133.5 

145.1 

10.6 

155.7 

146.0 

155.6 

.060 

.:  7i 

.170 

1.001 

0.20  | 

11.6 

133  0 

144.6 

11  4 

156.0 

145.5 

155.4 

.060 

1.767 

.183 

1  .01" 

0.20  1 

41.3 

11.5 

182  5 

114.0 

11.8 

155.8 

144.9 

154.9 

;  .060 

.766 

]826 

.189 

1  .015 

0.20 

82.1 

15.2 

128.0 

143.2 

8.3 

151.5 

144.4 

152.2 

!  .079 

.776 

.855 

.133 

.’■IK* 

0.20  ; 

32.1  , 

15.9 

14.7 

133.7 

124.0 

149.6 

138.7 

9.5 

9.8 

159.1 

148.5 

150.9 

139.9 

157.0 

149.4 

1.082 

i.076 

.810 

.750 

.892 

826 

.152 

.157 

1.044 

.<188 

14.7 

124.0 

138.7 

148.6 

139.9 

149.4 

.076 

.750 

.826 

.159 

.985 

0.20 

37.8 

Ellipse. 

15.3 

129.0 

144.3 

9.2 

153.5 

145.5 

158.0 

‘.079 

.781 

.860 

.147 

1.007 

0.10  | 

31.2  ; 

14.9 

126.0 

140.9 

9.8 

150.7 

142.1 

150.9 

.077 

.764 

.841 

.157 

.998 

| _ 

J.  Park. 


28  24  25  26 


Volume  of 
Voids  in 
1  Ci .  Ft. 


Modulus  of  Rupture. 


075  .156,  RS  8  i 

066  .148  02  j  2 

090  .169  92  j  8  I 

081  .162  91  !  8 

092  .171,  92  8 

1281.2001  91  2 

.045  . 155  91  8 

,021  .139  91  2 

.078;. 174  90  8 


026!  .124 
118  .169] 
122  .178, 

'4! 


884  2821  |  . 

292  188  (' .  i  Slightly  i 
289  ,  262  ;  270 


846!  801  f 
831  800  i 
305  270  \ 


Compressive  Strength. 


245  Surface  rocky. I  17; 


1  410  1  250  1  380 

1  7101  1  710  1  710 

1  180  1  090!  1  185 

I  495  1  410  1  455 

1  440,  1  816  1  375 

1  565  1  450,  1  505 

1  920  1  745  1  880 

1  715;  1  605  1  660 

1  795!  1  750  1  770 

1  370  1  680  |  500 

1  425  1  895  1  410 

1  100]  940  1  020 

965  916  040 


Note.— Volumes  cubic  feet  per  100  lbs.  as  mixed:  Cement,  1.00;  Jerome  Park  screenings  (Crusher  Run),  1.06;  Jerome  Park  stone,  1.08;  mixture  Jerome  Park  screenings  and  stone  varies  with  mixture;  Cowe  Bay  sand  (natural),  1.11;  Cowe  Bay 
ursvel,  0.97.  Specific  gravity:  Cement,  3.10;  Jerome  Park  screenings  varies  with  size;  Jerome  Park  stone,  2.78;  mixture  Jerome  Park  screenings  and  stone,  2.77;  Cowe  Bay  sand,  2.65;  Cowe  Bay  gravel,  2.05.  Weights  per  cubic  foot  as  mixed:  Cement. 
1 110;  Jerome  Park  screenings  (Crusher  Run),  94.8;  Jerome  Park  stone,  97.0;  mixture  Jerome  Park  screenings  and  stone  varies  with  mixture;  Cowe  Bay  sand  (natural),  9.90;  Cowe  Bay  gravel,  102.7.  Tensile  strength  cement,  pounds  per  square  inch:  Neal 
;  (lavs,  562  ;  28  days,  695;  8  months,  720. 

Col.  15  =  Col.  10  X  0.08  -f  Col.  12.  Col.  16  =  Col.  12  +  (Col.  24  x  62.4 ).  Col.  15  represents  theoretical  minimum  assuming  of  water  for  chemical  combination.  Col.  16  represents  theoretical  maximum,  assuming  voids  filled  with  water. 

*  Including  cement. 


TABLE  14  d. — Composition  and  Transverse  Strength  of  Concrete  Beams  Made  with  Different  Aggregates  of  Various  Analyses  Mixed  with  Different  Percentages 
of  Cement  Tested  at  Jerome  Park  Reservoir  by  the  Aqueduct  Commission  during  the  Year  1905.  Beams,  6  x  6  x  72  Inches.  Spans,  68  and  32 

Inches.  Giant  Portland  Cement.  Age,  90  Days. 


Compressive  Strength  of 
Concrete  Prisms,  6x6 
X  18  Inches.  Average 
Age,  140  I  >ays. 


23U 

281 

238 


3  |  4 

5 

6 

7 

b 

•o 

Itf 

ii 

1 

•L 

it 

f!  ° 

a  08  *§ 

1 

ii 

i"1 

If1 

|S  2 
o 

3 

ii 

£  05 

10.6  j  Cowe  Bay. 

Cowe  Bay. 

i  " 

0.10 

io!o 

I 

in  n 

nin* 

10.6 

r 

0.075 

10.6 

r 

10.6 

181 

2}" 

6.20 

15.9 

2J" 

0.20 

8.5 

2j- 

)*.2u 

10.6 

21" 

i )  20 

10.6 

21" 

0i20 

10.6 

0.10 

10.6  | 

1  " 

0.10 

10.2  J.  Park. 

“ 

21" 

0.20 

10.2 

.. 

2j" 

0.20 

10.2  “ 

21" 

0.20 

10.2 

2j" 

0.20 

10.2 

2J" 

10.2 

2j- 

======== 

=  -- . 

: - 

o6 


Ellipse. 

Ellipse. 


16  I  17  1  18  ]  19  |  20 


19.8 

23.0 

12.4 

I  15.8 
15.7 
!  15.1 
!  15.2 
14.6 
|  15.8 


148.4 
142.1 1 

143.4 


Calculated  Volume  ii 
Cubic  Feet  of 
Material  in  1  Cu.  Ft. 
of  Beam  as  Mixed. 


9.2  152.6  144.6,  152.5 


145.8  130.0  141 
148.lt  139.7  149.4 
155.0  147.2  154. 
154.0  146.6  153. 
155.2  146.6,  158.6 

168.6'  150.7  1 
157.0  149.7  155.6 

161.4  143.31  151.5 

153.5  144. o;  152.3 


142.9  10.2 
150.31  10.0 


153.1  144. lj  153.7 
160.3  151.5;  158.5 


173  1.005 
147!  1.002 
158!  .993 

165  .  992 


Volume  of 
Voids  in 
1  Cu.  Ft. 


i  1 

II- 


004 

.979  .  068 
.979  .  064 
1.014  .084 
1  .014  .1C.) 
1.025  .  054 


1.018  .067 
.990  .  064 


Modulus  of  Rupture. 


.196  90 
.175  90 
.185  90 
.183  »0 
.129  91 


039!.  108 
047  .116 
087|.153 
077] .144 
010  .174 
084  .181 


382  258  258 

2981  258  / 

232  214  f44" 

282  262  272 

225,  199  216 

170  170  I  | 

182  182  f178  ’ 

326  272  I I 

352  816  ;  ( 1 ' 

176  150  168  l. 

263  226  1)  052 


5  KM . j' 

270,  242  1  256  {Sort^very 

880  898  iSDrfaceyVerylt 

h  1 1 

270  I  I  I  slightly 

)  289  (  rocky. 

™  I  I  |  Surface  1 

J  I  rocky.  | 

210  i  172  1 


[  1 

,  2  j  8 

4 

1  6 

1  8 

t 

|  Comprks8ivk  Strength. 

;  1 

I  | 

Pounds 

a 

3 

per  square  inch. 

8 

8,  is 

a 

| 

• 

£ 

-  0 

E 

& 

1  - 

a 

3 

226 

146  2 

1  505 

1 545 

1  555 

227 

1  147  2 

2  005 

1 000 

1  660 

228 

I  146  2 

1  305 

1  1 85 

1  275 

235  | 

141  2 

1  ego 

1 

1  580 

259  ; 

IBS  2 

1  650 

1  575 

1  610 

286  j 

141  2 

1  205 

1  026 

1  145 

m 

141  2 

980 

895 

885 

221 

146  2 

2  110 

1  07" 

1  890 

146  2 

2  815 

1  7  <  W  > 

2  040 

288  i 

143  2 

1  045 

940 

990 

229  i 

143  2 

1  lift 

1  27U 

1  840 

280  j 

143  2 

1  790 

1  170 

1  480 

281 

143  2 

1  ;  (0 

1  185 

1  610 

282 

142j  2 

980 

1  0<10 

200 

141  2 

1  385 

1  280 

1  280 

209 

189 1  2 

1  685 

1  605 

1  620 

213 

1361  2 

2  000, 

1  800 

1  900 

214 

136 1  2 

1  925 

1  S26 

1  875 

205 

142  2 

1  480 

1  120 

1  800 

206 

1401  2 

1  435 

1  265 

1  350 

...oi  Noth.  Volumes,  cubic  feet  per  100  lbs.  as  mixed:  Cement.  1.00;  Jerome  Park  screenings  (Crusher  Run).  1.06:  Jerome  Park  stone.  1.03;  mixture  Jerome  Park  screenings  and  stone  varies  with  mixture:  Cowe  Bav  sand  (natural).  1.11;  Cowe  Bav 
„  *™vuy :  ^em«nt •  839:  Jerome  Park  screenings  varies  with  size:  Jerome  Park  stone,  2.78;  mixture  Jerome  Park  screenings  and  stone.  2.77;  Cowe  Bay  sand,  2.65:  Cowe  Bay  gravel,  2.65.  Weights  per  cubic  toot  as  mixed  :  Cement. 

.irllHUu  K  SlrccUinffS  (  Lrusllpr  Klin  >  H*  lAPiime  Pori*  ctnna  07  IV  mivfnpo  Tammo  PopI-  e/muMiinoc  and  afnna  uapiac  nritV  mivtneA-  D^..  ,.n  n  d  /nntiunl  )  O  O  i.  Dr, ,,  »M»nal  1 0f)  r7  'Tnnnllc  ■  ■  «  ’ 

,  7  days,  562;  28  days,  696;  8  months.  720. 

Col.  15  =  Col.  10  X  0.08  4-  Col.  12.  Ci 


*  Including  cement 


Col.  12.  Col.  10  =  Col.  12  -4-  (Col.  24  x  62.4).  Col.  15  represents  theoretical  minimum,  assuming  8-V  of  water  for  chemical  combination.  Col.  16  represents  theoretical  maximum,  assuming  voids  filled  with  water. 


TA^nalyses  Mixed  with 
Year  1905. 


dulus  of  Rupture. 


210 

199 

144 

146 

148 

149 

155 

157 

150 

156 

158 

145 

147 

151 

152 

159 

160 


26  27 


28  29 


Pounds 

per  square  inch. 


177 


282 

278 


284 

258 


282 


2  26 

280 
240 
222, 
223 1 

....I 


929 

744 

248 

231 

246 

253 

244 

199 

246 

248 

201 

241 

222 

209 

203 

198 


j-919 

276 

251 

265 

269 

] 

j-243 

J 

269 

{■247 


212 


30 


Surface  rocky. 
Excess  of 
fine  sand. 
Surface  rocky. 
Very  rocky. 
Surface 
very  rocky. 

I  Surface 
[  rocky. 

Surface  rocky. 


Surface  rocky. 


Compressive  Strength 
of  Concrete  Prisms, 
6  X  6  X  18  Inches. 
Average  Age,  140 
Days. 


1 

2 

3 

4 

5 

1  6 

Compressive  Strength. 

u 

% 

8 

p 

S3 

Pounds 

CQ 

per  square  inch. 

© 

© 

a 

<x> 

Age. 

£ 

r© 

a 

0 

a 

p 

® 

bo 

Sh 

© 

© 

Pn 

O 

o' 

a 

1 

3 

a 

•a 

§ 

© 

> 

< 

210 

199 

144 

146 

148 

149 

154 

1 

1  310 

1  310 

1  310 

155 

142 

3 

1  580 

1  250 

1  425 

157 

142 

3 

1  490 

1  305 

1  425 

150 

149 

1 

1  405 

1  405 

1  405 

156 

142 

2 

1  325 

1  235 

1  280 

158 

145 

141 

2 

1  225 

1  185 

1  205 

147 

151 

147 

2 

1  155 

1  015 

1  085 

152 

147 

2 

1  060 

980 

1  020 

159 

141 

2 

920 

795 

855 

160 

141 

2 

895 

785 

840 

Compressive  Strength 

TABLE  14  a. _ Composition  and  Transverse  Strength  of  Concrete  Beams  Made  with  Different  Aggregates  of  Various  Analyses  Mixed  with  of  Concrete  Prisms, 

Different  Percentages  of  Cement,  Tested  at  Jerome  Park  Reservoir  by  the  Aqueduct  Commission  during  the  Year  1905.  6  X  6  X  18  Inches. 

Beams,  6  X  6  X  72  Inches.  Spans,  68  and  32  Inches.  Giant  Portland  Cement.  Age,  90  Days.  Average  Age,  140 

Days. 


2 

8 

4 

5 

6 

7 

8 

9 

10 

11  j  12 

13 

14 

15  j 

16 

17  18 

19  1  20 

21 

22 

23 

24 

25  1 

26 

27  1 

28 

29 

so 

2  | 

8: 

4  1 

5  1 

6 

Proportions  by 
weight. 

Cement  to  total  dry  1 
materials,  X. 

o 

a 

1 

o 

2 

1  Maximum  size  of 
stone. 

(  Uniformly  graded 
above  diameter, 
inches. 

Per  cent,  finer  than 
diameter  in  Col.  7.* 

Curve  below 
diameter  in  Col.  7.t 

Weight  in  Lbs.  of  Materials  in  1 
Ft.  of  Beau  as  Mixed. 

Cu. 

Calculated  Volume  in 
Cubic  Feet  of 
Material  in  1  Cu.  Ft. 
of  Beam  as  Mixed. 

Volume  of 
Voids  in 

1  Cu.  Ft. 

Modulus  of 

Rupture. 

Remarks. 

|  Reference  numbers.  | 

Compressive  Strength. 

Pounds 

per  square  inch. 

Age. 

No.  of  breaks.  | 

Pounds 

per  square  inch. 

Cement. 

j  Aggregate. 

|  Total 

dry  mixed. 

H 

eC 

Totals. 

j  As  mixed. 

|  Minimum. 

|  Maximum.  | 

1  Cement. 

1  Aggregate. 

Total  dry. 

Water. 

i 

5 

Aggregate. 

Total.  1 

Age,  days 

1 

o' 

i 

|  Maximum. 

Minimum. 

1 

Average,  j 

Maximum. 

Minimum. 

Average.  | 

Neat. 

104.5 

00.0  104.5 

29.6 

134.1 

112.9 

133.1 

.541  .000 

.541  .475 

1.016 

.459 

.000 

.459 

5.89 

8 

1  177 

929 

1-919 

210 

. 

1:9 

10 

J.  Park. 

J.  Park. 

2  i" 

0.10 

29.9 

Parabola. 

15.0 

00.0  100.5 
135  0  150.0 

10.2 

160 !  2 

1U3.0  13U.4 

151. 2\  158.9 

.520  .  000 
.078  .7.80 

.520  .  487 
.858: .16S 

1 .007 
1.021 

.480 

.066 

.000 

.076 

.480 

.142 

91 

90 

3 

303 

248 

276 

Surface  rocky. 

199  1 
144 

:::::: 

1:9 

10 

8i" 

0.10 

31.4 

15.4 

138.2  153.6 

9.3 

162.9 

154.8 

166.1 

.080!  .799 

.879  .149 

1.028 

.067 

.054 

.121 

90 

3 

266 

231 

251 

1  Excess  of 

146 

. 

1:9 

10 

2j" 

0.20 

35.8 

Ellipse. 

15.0 

135.0  150.0 

10.2 

160.2 

151.2 

158.9 

.078  .  780 

.858  .163 

1.021 

.066 

1.076 

.142 

90 

3 

282 

246 

265 

Surface  rocky. 

148 

1 

1  810 

1  810 

1  810 

1:9 

10 

2}" 

0.20$ 

36. 9t 

“  * 

14.9 

138.7  148.6 

9.9 

158.5 

149.8 

158.0 

.077  .  772 

.849  .159 

1.008 

.065 

.086 

.151 

91 

2 

278 

258 

269 

1 

Very  rocky. 

(  Surface 

149 

I.'64 

1:9 

10 

2}” 

0.20 

37.8 

15.0 

134.5:  149.5 

10.8 

160.3 

150.6  158.5 

.078  .  777 

.855  .173 

1,028 

.006 

.079 

.145 

90 

3 

284 

244 

J  very  rocky. 

155  1 

142 

3 

1  580 

1  250 

1  425 

1:9 

10 

2i" 

0.20 

37.8 

14.9 

134.01  148.9 

10.0 

158.9 

150.1 

158.1 

.077'  .775 

.852  .160 

1.012 

.065 

.083 

.148 

90 

8 

258 

199 

]  Surface 

157 

142 

3 

1  490 

1  305 

1  426 

J 

{  roeky. 

1:9 

10 

2j" 

0.20$ 

38. 6t 

“  t 

14.8 

133.3  148.1 

8.9 

157.0 

149.3  157.6 

.076!  .771 

.847  .143 

.990 

.064 

.089 

.153 

91 

2 

293 

246 

269 

150 

149 

1 

1  406 

1  405 

1  405 

1:9 

10 

2  r 

0.20 

39.4 

14.6 

181.2  145.8 

'•‘.6 

155.4 

147.0 

156. 3 

.075  .  757 

.832  .153 

.985 

.064 

.104 

.168 

90 

3 

282 

248 

Surface  rocky. 

156 

142 

2 

i  :i2f, 

1  285 

1  280 

1:9 

10 

2r 

0.20 

39.4 

14.5 

131.0  145.5 

9.8 

155.3 

146.7 

156.0 

.075  .  757 

.832  .157 

.989 

.064 

.104 

.168 

90 

3 

25 1 

201 

158 

141 

2 

1  225 

1  185 

1  205 

1:9 

10 

1 " 

0.10 

34.2 

Parabola. 

14.3 

129.01  143.3 

11.8 

155.1 

144.4 

155.8 

.074  .  725 

.7991.189 

.988 

.063 

!.138 

.201 

90 

286 

241 

264 

145 

1:9 

10 

1  " 

0.10 

35.0 

14.4 

130.1  144.5 

9.9 

154.4 

145.7 

155.2 

.075  .753 

.828. 159 

.987 

.064 

.108 

.172 

90 

2 

220 

222 

224 

147 

1:9 

10 

0.10 

35.9 

Ellipse. 

14.3 

129.0  143.3 

11.9 

155.2 

144.4 

154.5 

.075  .745 

1 

.820  .191 

1,011 

.064 

.116 

.180 

90 

3 

230 

209 

151 

147 

2 

1  155 

1  015 

1  1  086 

10 

0.10 

35.9 

14.3 

129.0  143.3 

11.9 

155.2 

144.4  1  54.5 

.075  .  745 

.820  .191 

1.011 

.0641.116 

.180 

90 

3 

240 

203 

152 

147 

2 

1  060 

980 

1  020 

1:9 

10 

0.10 

37.7 

13.9 

124.8  138.7 

12.8 

151.5 

139.8 

151.6 

.072  .720 

.792  .205 

.997 

.061 

.147 

.208 

90 

2 

222 

198 

Surface  rocky. 

159 

141 

2 

920 

795 

856 

1:0 

10 

1  " 

0.10 

37.7 

M.O 

125.5  139.5 

13.8 

153.3 

140.6 

152.1 

.0731.725 

.798  .221 

1.019 

.062 

!  .140 

.202 

90 

2 

223 

202 

s 21 

160 

141 

2 

89S 

785 

840 

1:9 

10 

i" 

0.075 

36.3 

13.4 

120.8  134.2 

12.9 

147.1 

135.3 

148.7 

.069  .698 

.767'  .207 

.974 

.059 

1  .174 

.233 

91 

2 

174 

172 

j 

104 

137 

2 

m 

i  770 

800 

1:9 

10 

l" 

0.075 

36.3 

13.5 

121.2  134.7 

13.0 

147.7 

135.8  149.0 

.070  .  700 

.770  .208 

.978 

.057 

.171 

.230 

91 

3 

2-:*J 

198 

Surface  rocky. 

165 

187 

2 

96E 

i  955 

I  900 

1:9 

10 

i" 

0.075 

38.2 

13.3 

120.2  183.5 

12.8 

146.3 

134.61  148.2 

1 

.069  .695 

.764  .205 

.969 

.059 

1  .177 

.236 

90 

3 

273 

195 

208 

153 

181 

2 

89E 

>  85C 

1  870 

Note.— Volumes,  cubic  feet  per  100  lbs.  as  mixed:  Cement,  1.00;  Jerome  Park  screenings  (Crusher  Run).  1.0G;  Jerome  Park  stone,  1.03;  mixture  Jerome  Park  screenings  and  stone  varies  with  mixture;  Cowe  Bay  sand  (natural),  1.11;  Cowe  Bay 
gravel,  0.97.  Specific  gravity:  Cement,  3.10;  Jerome  Park  screenings  varies  with  size;  Jerome  Park  stone.  2.78;  mixture  Jerome  Park  screenings  and  stone,  2.77;  Cowe  Bay  sand,  2.65;  Cowe  Bay  gravel,  2.66.  weights  per  cubic  foot  as  mixed:  Cement, 
1,00;  Jerome  Park  screenings  (Crusher  Run),  94.8;  Jerome  Park  stone,  97.0;  mixture  Jerome  Park  screenings  and  stone  varies  with  mixture;  Cowe  Bay  sand  (natural),  0.90;  Cowe  Bay  gravel,  10.27.  Tensile  (strength  cement,  pounds  per  square  inch: 
Neat,  7  days,  562:  28  days,  695;  8  mouths,  720. 

Col.  15  =  Col.  10  X  0.08  +  Col.  12.  Col.  16  =  Col.  12  +  (Col.  24  x  62.4).  Col.  15  represents  theoretical  minimum,  assuming  8 X  of  water  for  chemical  combination.  Col.  16  represents  theoretical  maximum,  assuming  voids  filled  with  water. 

*  Including  cement,  t  See  separate  table  for  equations.  t.Not  an  ideal  ellipse.  (Per  cent,  on  0.20  ordinate  is  giveD  for  comparison  with  other  curves,  but  tangent  point  is  at  about  0.29.) 


Compressive  Strength 

TABLE  14  b. — Composition  and  Transverse  Strength  of  Concrete  Beams  Made  with  Different  Aggregates  of  Various  Analyses  Mixed  with  of  Concrete  Prisms, 
Different  Percentages  of  Cement,  Tested  at  Jerome  Park  Reservoir  by  the  Aqueduct  Commission  during  toe  Year  1905.  6  X  6  X  18  Inches. 

Beams,  6  X  6  X  72  Inches.  Spans,  68  and  32  Inches.  Giant  Portland  Cement.  Age,  90  Days.  Average  Age,  140 

Days. 


2 

3  |  4 

5 

6  i 

7 

8  I 

9 

10  | 

11  1 

|  >2  i 

13  j 

14  ! 

15 

16 

17 

18  | 

19 

20  j 

21  i 

22 

23 

24 

25  | 

26 

27  | 

28 

29 

80 

1 

2 

I8 

1  4 

1  5 

1  6 

Proportions  by 
weight. 

1  Cement  to  total  dry 

materials, . 

Kind  of  stone. 

1 

© 

p 

a 

I  Maximum  size  of 

stone. 

1  Uniformly  graded  i 

above  diameter, 
inches. 

1  Per  cent,  finer  than 

diameter  in  Col  7.* 

Curve  below 
diameter  in  Col.  7.+ 

Weight  in  Lbs.  of  Materials  in  1 
Ft.  of  Beam  as  Mixed. 

Cu. 

Calculated  Volume  in 
Cubic  Feet  of 
Material  in  1  Cu.  Ft. 
of  Beam  as  Mixed. 

Volume  of 
Voids  in 

1  Cu.  Ft. 

Modul 

US  OF 

Rupture. 

Remarks. 

j  Reference  numbers,  j 

Compressive  Strength. 

Age,  days. 

!  No.  of  breaks. 

Pounds 
per  square 

1 

inch. 

1 

|  No.  of  breaks. 

Pounds 

per  square  Inch. 

l 

6 

bl 

1 

4 

|  Total  dry  mix. 

cij 

£ 

Totals. 

1 

3 

| 

f 

eg 

s 

1 

O 

!  Aggregate.  | 

Total  dry.  j 

|  Water. 

1 

£ 

j  Cement.  1 

|  Aggregate.  | 

3 

& 

|  Maximum,  j 

|  Minimum. 

j  Average. 

J  Maximum. 

|  Minimum. 

|  Average. 

1:9 

10 

J.  Park. 

J.  Park. 

J- 

0.075 

38.2 

Ellipse. 

13.7 

123.0 

136.7 

13.2 

149.9 

137.8 

150.4 

.071 

.710 

.781 

.212 

.993 

.060 

.159 

.219 

90 

3 

212 

197 

208 

154 

142 

2 

890 

870 

880 

1:9 

10 

i” 

0.075 

39.8  | 

13.3 

119.5 

132.8 

14.6 

147.4 

133.9 

147.8 

1.069 

.690 

. 

.234 

.993 

.058 

.  183 

.241 

90 

8 

25S 

218 

195 

185 

2 

1  005 

1  015 

1:9 

10 

“ 

“ 

1” 

0.075 

39.8  , 

13.3 

119.5 

132.8 

14.4 

147.2 

133.9 

147.8 

.069 

.690 

.759 

.231 

.990 

.058 

.183 

.241 

90 

2 

305 

205 

J227 

190 

135 

2 

1  015 

910 

905 

1:2*  :6s 

10 

- 

2J” 

!  14.6 

131.3 

145.9 

9.6 

155.5 

147.1 

156.8 

.076 

.758 

.884 

.154 

.988 

.064 

.  1  <  >2 

.  166 

90 

8 

207 

$76 

| 

168 

135 

2 

786 

800 

1:2*  :6* 

1 0 

“ 

2)" 

|  14.4 

130.0 

144.4 

10.7 

155.1 

145.6 

155.3 

.075 

.751 

.m 

.172 

.998 

.064 

.110 

.174 

90 

3 

201 

161* 

135 

2 

990 

901) 

910 

1:8:6 

10 

2j- 

:::::::::::: 

!  14.2 

127.7 

141.9 

8.9 

150.8 

143.0 

153.7 

.074 

.737 

.811 

.143 

.954 

.063 

.126 

.189 

91 

3 

311 

225 

166 

137 

2 

1  210 

i  000 

1  185 

1:8:6 

10 

2J- 

. 

1  14.2 

127.8 

142.0 

9.0 

151.0 

143.1 

153.2 

.074 

.738 

.812 

.144 

.950 

.063 

.117 

.iso 

90 

1 

224 

224 

]  ^ 

107 

136 

2 

1  065 

965 

1  015 

1:9*  :6* 

10 

.. 

1  •• 

14.2 

127.8 

140.0 

14.6 

156.6 

141.1 

151.5 

.074 

.736 

.810 

.232 

1.042 

.063 

.121 

.184 

90 

2 

168 

138 

| 

172 

148 

2 

875 

855 

865 

1:8»:6* 

10 

1  " 

14.1 

127.2 

141.3 

11.2 

152.5 

142.4 

153.3 

.073 

.735 

.808 

1 180 

.988 

.062 

130 

192 

91 

2 

187 

ill 

1  15 

173 

145 

i  2 

905 

711) 

855 

1:8:6 

10 

j  14.0 

126.3 

140.3 

14.0 

154.8 

141.4 

152.6 

.072 

.730 

.802 

.226 

1.028 

.061 

.137 

r> 

90 

3 

1  Mi 

170 

188 

2 

920 

800 

890 

1:3:6 

10 

1  " 

!  13.8 

125.4 

139.2 

12.5 

151.7 

140.3 

151.9 

.071 

.725 

.796 

.200 

.996 

.060 

.144 

.204 

90 

3 

199 

160 

( 176 

171 

138 

2 

845 

850 

1:8*  :5? 

10 

1  " 

13.7 

123.4 

137.1 

13.6 

150.7 

138.2 

150.6 

.071 

.713 

.784 

.218 

1.002 

.060 

.156 

.216 

91 

3 

192 

166 

j 

174 

145 

2 

890 

795 

845 

l;8*:5* 

10 

13.8 

124.0 

137.8 

13.2 

151.0 

138.9 

151.2 

.071 

.715 

.786 

.211 

.997 

.060 

.154 

.214 

91 

3 

227 

171 

175 

145 

2 

980 

875 

930 

1:2*:6* 

10 

4" 

i  13.5 

121.9 

135.4 

14.0 

149.4 

136.5 

149.6 

.070 

.703 

.773 

.224 

.997 

.059 

1.168 

M 

90 

3 

211 

191 

204 

Siightly  rocky. 

192 

187 

2 

i  106 

875 

990 

1:8:6 

10 

J" 

1  18.5 

121.6 

1  135.1 

12.4 

147.5 

136.2 

149.3 

.070 

.702 

.772 

.199 

.971 

.059 

.169 

.228 

88 

2 

13.5 

100 

176 

143 

2 

090 

070 

680 

1:8:6 

10 

r 

13.5 

121.0 

|  134.5 

13.5 

148.0 

135.6 

148.9 

.070  .  700 

.770 

.216 

.986 

.059 

.171 

.230 

88 

8 

175 

169 

f 15 

177 

143 

2 

885 

740 

790 

1:8* :5* 

10 

4" 

"ZZ 

18.3 

119.3 

i  132.6 

14.4 

147.0 

133.7 

1  147.7 

.069 

.689 

.758 

.231 

.989 

.059 

.183 

.242 

90 

8 

156 

145 

152 

194 

135 

2 

830 

815 

825 

1:9  Uniform  stone. 

10 

21" 

,'20" 

87.8 

Ellipse. 

14.9 

134.0 

i  148.9 

9.6 

158.5 

150.1 

158.1 

.077 

.775 

.852 

.154 

1.006 

.065 

.083 

.148 

90 

2 

269 

244 

257 

Slightly  rocky. 

187 

141 

2 

i  086 

1  105 

1  350 

i  i;0  “  »» 

10 

1  " 

.10 

87.7 

|  13.9 

195.fi 

1  139.5 

12.8 

152.3 

140.6 

152.2 

.072 

.725 

.797 

.205 

1.002 

.061 

.142 

.203 

90 

2 

230 

229 

188 

141 

'.*70 

915 

950 

l  1  i;0  u  »» 

10 

r 

.075 

39.8 

l  “ 

1  134 

121. C 

l  134.4 

14.3 

148.7 

135.5 

148.8 

1  .069 

.700 

.769 

.229 

.998 

.069 

.172 

.231 

91 

2 

181 

179 

180 

198 

145 

2 

900 

875 

890 

Note —Volumes;  cubic  feet  per  100  lbs.  us  mixed:  Cement,  1.00;  Jerome  Park  screenings  (Crusher  Run).  1.06;  Jerome  Park  stone,  1.03;  mixture  Jerome  Park  screenings  and  stone  varies  with  mixture;  Cowe  Bay  sand  (natural),  1.11;  Cowe 
Bay  gravel ,0.97.  Specific  gravity:  Cement,  3.10;  Jerome  Park  screenings  varies  with  size;  Jerome  Park  stone,  2.78;  mixture  Jerome  Park  screenings  and  stone,  2.77;  Cowe  Bay  sand,  2.65;  Cowe  Bay  gravel,  2.65.  Weights  per  cubic  foot  as  mixed: 
l  enient,  1.00:  Jerome  Park  screenings  t,  Crusher  Ruu),  W.8;  Jerome  Park  stone,  97.0;  mixture  Jerome  Park  screenings  and  stone  varies  with  mixture;  Cowe  Bay  sand  (natural),  0.90;  Cowe  Bay  gravel,  10.27.  Tensile  strength  cement,  pounds  per  square 
iueh:  Neat,  T  days,  5(53;  S3  days,  6115;  8  months,  720. 

*  T  *  ,  Tt  10  x  +  Col.  12.  Col.  16  =  Col.  12  4-  (Col.  24  x  62.4).  Col.  15  represents  theoretical  minimum,  assuming  8%  of  water  for  chemical  combination.  Col.  16  represents  theoretical  maximum,  assuming  voids  filled  with  water. 

*  Including  cement.  $  Omitted  in  average. 


Column  23  is  the  difference  between  columns  24  and  22. 

In  determining  the  average  strength  of  each  mixture,  column  29, 
all  of  the  breaks  of  the  two  beams,  which  are  in  duplicate,  are  aver¬ 
aged,  that  is,  if  one  of  a  pair  of  beams  has  only  two  breaks,  while  the 
other  has  three,  the  five  breaking  strengths  are  added  together,  and 
divided  by  five,  instead  of  assuming  that  the  two  breaks  give  the 
I  average  of  one  beam  and  the  three  breaks  the  average  of  the  other 
beam.  The  method  followed  is  considered  more  accurate  than  the 
other,  because  a  beam  which  can  be  broken  only  once  or  twice  is 

■  possibly  imperfect,  and  therefore  this  beam  should  not  have  quite  so 
1  large  a  place  in  the  average  as  the  beam  with  three  breaks. 

The  compressive  strength  of  the  concrete  prisms  made  by  capping 
ft  two  pieces  of  each  beam  are  given  at  the  right-hand  of  each  sheet  of 
t  Table  14.  These  prisms  were  broken  by  Prof.  Frederick  L.  Pryor  at 
I  the  Stevens  Institute  of  Technology,  Hoboken,  N.  J.,  and  although 
j  the  heads  of  the  machine  were  fixed,  the  ends  of  the  specimen  were 
sufficiently  parallel  to  give  good  results,  nearly  all  the  pieces  break- 
I  ing  in  a  manner  normal  to  long  prisms.  The  breaks,  as  is  usual 
i  with  such  specimens,  were  more  longitudinal  than  is  the  case  with 
[cubes,  where  two  pyramids  are  generally  formed  with  their  bases 

■  against  the  heads  of  the  machine. 


■  Comparative  Density  and  Strength  of  Beams  Made  with  Dif¬ 
ferent  Brands  of  Cement. 

Table  15  gives  the  results  of  tests  of  neat  cement  beams,  and  of 
concrete,  made  with  a  number  of  brands  of  cement  selected  as  repre¬ 
sentative  of  different  sections  of  the  United  States.  The  samples  of 
these  cements  were  purchased  a  year  before  testing,  and  on  this 
account  the  relative  results  may  be  questioned  somewhat.  How¬ 
ever,  as  the  cements  were  packed  in  barrels  and  stored  in  the  labora¬ 
tory  at  Jerome  Park,  it  is  probable  that  the  results  are  equal  to  that 
which  would  be  obtained  from  fresher  samples.  The  results  indicate 
that  the  Giant  cement  used  in  the  1905  experiments  is  equal  to  any 
of  the  other  brands,  and  has  normal  density.  A  comparison  of  the 
density  of  the  neat  beams  of  Giant  cement  in  Table  15  with  the 
density  of  the  neat  beams  of  the  same  brand  tested  in  1904  shows  a 
much  greater  density  for  the  1905  cement.  The  average  density  of 


74 


the  latter  in  the  neat  beams  is  about  0.53,  while  the  density  is  about 
0.49  in  the  1904  tests.  The  effect  of  increased  density  of  any  cement 
upon  its  real  value  has  yet  to  be  determined,  but  a  comparison  of  the 
two  series  of  tests  shows  in  this  case  that  the  cement  giving  paste  of 
the  less  density  produced  the  poorer  concrete. 


Permeability  Tests. 

The  results  of  the  permeability  tests  have  emphasized  the  fact  of 
how  little  is  known  of  the  action  of  concrete  in  resisting  the  flow  of 
water.  Examination  of  the  tests,  which  are  given  in  full,  Table  16, 
indicates  in  general  that,  using  different  proportions  and  different 
sizes  of  the  same  class  of  materials,  the  laws  of  water-tightness  are 
somewhat  similar  to  those  of  strength;  If  the  percentage  of  cement 
be  the  same  the  specimens  having  the  greatest  density  are  usually 
most  water-tight,  and  in  the  specimens  having  similar  density  but 
different  percentages  of  cement,  the  water-tightness  increases  with 
the  percentages  of  cement.  The  ratios,  however,  are  very  different 
from  the  ratios  of  either  density  or  strength,  a  slight  difference  in 
the  composition  producing  a  tremendous  effect  upon  the  water¬ 
tightness.  Different  kinds  of  aggregate  also,  for  reasons  not  yet  ex¬ 
plained,  produce  very  different  results  in  water-tightness.  The 
results  of  the  tests  are  discussed  in  detail  on  pages  78  to  83.  An 
important  result  of  the  permeability  tests  has  been  the  evolution  of 
an  apparatus,  described  in  succeeding  paragraphs,  by  means  of  which 
almost  any  character,  shape  or  thickness  of  specimen  may  be  sub¬ 
mitted  to  water  pressure.  The  advantages  of  the  apparatus  lie  in 
the  exposure  of  the  entire  top  surface  of  the  specimen  to  the  water 
pressure,  the  coating  of  the  sides  of  the  specimen  with  neat  cement 
so  as  to  confine  the  flow,  and  the  discharge  of  the  water  through  the 
bottom  of  the  specimen. 

Method  of  Making  Permeability  Tests. 

The  apparatus  used  in  making  permeability  tests  and  the  prepara¬ 
tion  of  the  specimen  is  indicated  in  Figs.  21  and  22.  The  method 
of  preparing  the  specimen  which  was  found  satisfactory  after  a 
number  of  trials  is  illustrated  in  Fig.  21.  A  piece  of  a  concrete 
beam,  about  6  in.  square  and  17  in.  long,  obtained  by  breaking  the 


75 


‘beam  in  the  regular  manner  in  the  testing  machine,  is  scored  over 
the  surface  of  its  four  sides  by  a  hammer  and  cold  chisel,  so  as  to 
give  rough  and  uneven  surfaces  and  afford  a  better  adhesion  to  the 
cement  coating.  The  specimen  is  then  immersed  in  a  can  of  water 
and  soaked  for  24  hours.  It  is  then  taken  from  the  water,  placed  in 
a  wooden  mold  so  constructed  that  the  specimen  can  set  upright  in 
it,  and  leave  a  space  on  the  four  sides,  and  a  mound  of  sand  is 
formed  on  the  top  and  held  in  place  by  a  wood  strip,  first  thoroughly 
soaked  with  water.  The  surface  of  the  sand  is  covered  with  a  piece 


Fig.  21.— Method  of  Preparing  Specimen  for  Permeability  Test. 

of  tissue  paper  to  prevent  the  cement  flowing  into  it.  1  000  grammes 
of  fine  sand  which  passes  a  No.  30  sieve  and  is  caught  on  a  No.  40 
are  required.  On  top  of  the  sand  is  placed  a  4-in.  iron  flange  with  a 
i-in.  nipple  4|  in.  long  screwed  into  it  and  made  up  in  a  tight  joint 
so  that  there  can  be  no  leakage  along  the  thread. 

Neat  cement  mixed  to  a  paste  about  as  stiff  as  can  be  conveni¬ 
ently  handled  and  compacted,  is  poured  into  the  mold  around  the 
specimen  and  over  the  sand,  thus  forming  a  dome  above  it.  About 


76 


83  lb.  of  cement  and  21  lb.  of  water  are  used  for  the  casing*.  When 
pouring  the  cement  four  pieces  of  |-in.  galvanized  ribbon  wire  or 
some  other  form  of  reinforcing  metal  are  placed  in  pairs,  two  at 
right  angles  to  the  other  two,  over  the  top  of  the  specimen  and  down 
along  the  side,  as  shown  in  Fig.  21,  page  75,  to  reinforce  the  cement 
and  prevent  the  blowing  off  of  the  dome,  which  occurred  in  one  of 
the  experimental  tests.  As  the  cement  is  compacted,  water  rises- 
to  the  surface  and  bubbles  of  air  come  up  through  the  cement  and 
water.  The  casing  is  not  considered  complete  until  this  bubbling 
ceases.  The  surface  of  the  specimen,  after  it  is  complete,  is  covered 
with  miost  sand,  and  this  is  kept  wet  by  a  very  slow  flow  from  a 
water  cooler.  At  the  end  of  24  hours,  the  neat  cement  has  thor¬ 
oughly  set,  and  the  specimen  can  be  removed  from  the  mold  and 
buried  in  damp  sand  until  ready  to  test. 

Apparatus  for  Testing  Permeability. — The  apparatus  for  testing, 
together  with  the  specimen  itself,  is  shown  in  Fig.  22.  The  speci¬ 
men  is  placed  upon  a  tin  funnel,  set  in  a  wooden  frame  which  rests 
upon  any  suitable  foundation.  The  pipe  projecting  through  the  top 
of  the  specimen  is  connected  by  a  union  coupling  with  the  bottom 
of  the  air  pressure  tank,  which  is  nearly  filled  with  water  before  be¬ 
ginning  the  test.  The  pressure  is  raised  by  the  hand  pressure  air 
pump  shown  in  the  photograph,  and  maintained  at  any  desired*  pres¬ 
sure  for  any  required  period.  The  time  is  read  by  a  stop-watch  read¬ 
ing  for  convenience  to  hundredths  of  minutes,  instead  of  to  sec¬ 
onds,  which  is  started  at  the  beginning  of  the  tests,  and  allowed  to 
run  as  long  as  the  experiment  is  continued.  The  water  is  caught 
in  a  bottle  placed  below  the  funnel  under  the  specimen,  and  weighed 
at  intervals  by  substituting  a  second  bottle. 

Recording  the  Data. — The  method  of  recording  the  data  of  the 
tests  is  shown  in  a  typical  form.  Table  17.  Convenient  periods  of 
flow  for  most  of  the  specimens  were  found  to  be  five  minute  inter¬ 
vals,  this  giving  sufficient  time  to  weigh  the  bottle,  and  being  fre¬ 
quent  enough  to  obtain  the  average  rates  of  flow.  It  was  found  that 
about  five  minutes  were  required  for  the  flow  at  any  given  pressure 
to  become  constant,  and  therefore  the  flow  during  the  first  five  min¬ 
utes  at  any  given  pressure  is  not  included  in  figuring  the  average 
flow. 


Fig.  22.— Apparatus  for  Testing  Permeability  of  Concrete. 


c* 

Rate  op  Flow  of 
Water,,  Grams 
per  Min. 

•m  -bs 

aad  -sq[  08  1Y 

|  SS‘8‘83  : 

*  Including  cement. 

this  and  the  Jerome  Park  mateilalf61*0611^^6  C6ment  ^  ^ncrease(^ ,a  ea(^h  case  to  balance  the  difference  in  specific  gravity  between 

8 

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Calculated  Volume  in  Cubic 
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Cubic  Foot  op  Beam  as 
Made. 

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1.011 

.978 

.988 

.956 

1.042 

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1.006 

1.001 

1.041 

1.031 

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78 


Adhesion  of  Cement  Costing  to  C oncrete  Bloch. — The  only  possi¬ 
bility  of  a  leakage  which  is  not  immediately  apparent  is  between  the 
specimen  and  the  neat  cement  casing.  In  order  to  prove  that  the 
adhesion  was  perfect,  several  specimens  were  broken  after  the  com¬ 
pletion  of  the  tests.  One  of  the  first  specimens  showed  signs  of 
slight  percolation  between  the  specimen  and  coating,  but  by  more 
carefully  roughening  the  surface  before  coating,  this  was  entirely 
prevented  in  subsequent  tests,  and  the  bond  of  union  was  found  to 
be  absolutely  perfect,  the  adhesion  of  the  cement  casing  to  the  con¬ 
crete  being  stronger  than  the  adhesion  of  the  ingredients  of  the 
concrete. 

Results  of  Permeability  Tests. 

An  examination  of  Table  16  reveals  a  number  of  points  which 
stand  out  very  clearly  in  the  results  and  form  the  basis  for  the  con¬ 
clusions  on  the  following  pages.  To  establish  definite  laws  and  com¬ 
pare  materials  not  included  in  this  series  of  tests,  further  experi¬ 
ments  are  essential.  The  permeability  of  the  different  specimens  is 
indicated  in  columns  18  to  21  by  the  rate  of  flow  in  grammes  per 
minute  at  different  pressures.  The  specimens  are  all  of  approxi¬ 
mately  the  same  length,  namely,  17  in.,  and  the  flow  is  through  this 
total  length. 


Effect  of  Per  Cent,  of  Cement  Upon  Permeability. 

Compare  in  Table  16,  in  the  following  order,  specimens  193, 
155,  179,  and  183,  also  specimens  233,  217,  224,  225,  also  specimens 
213,  218  and  216.  It  is  seen  that  the  rate  of  flow  is  less  as  the  per¬ 
cent  of  cement  increases  and  in  a  much  larger  inverse  ratio.  The 
most  extreme  differences  are  shown  in  the  straight  Jerome  Park 
materials,  with  which  the  rate  of  flow  at  80  lb.  pressure  decreases 
from  273  grammes  per  minute  in  the  specimens  having  8%  of  ce¬ 
ment  to  12  grammes  per  minute,  in  the  specimen  having  15%  cement. 

Effect  of  Size  of  Stone  Upon  Permeability. 

Comparing  in  Table  16,  in  the  following  order,  specimens  No. 
205,  203  and  207,  also  specimens  221  and  227,  it  is  seen  that  the  rate 


of  flow  is  less  as  the  maximum  size  of  the  aggregate  is  greater. 
Specimens  of  straight  Jerome  Park  material,  No.  155,  151  and 
165,  apparently  do  not  agree  with  this  conclusion,  concrete 
with  the  1-in.  and  |-in.  stone  giving  about  the  same  rate  of  flow, 
and  the  2|-in.  stone  giving  greater  than  either  of  the  smaller  sizes, 
but  the  results  are  much  less  definite  than  those  of  the  other  tests 
mentioned.  All  the  straight  Jerome  Park  specimens,  in  fact,  are 
more  erratic  as  regards  permeability  than  the  specimens  containing 
more  rounded  grains  which  can  be  more  uniformly  mixed. 


TABLE  17.— Form  for  Permeability  Tests. 


Specimen  No.  165. — Maximum  Size  of  Stone,  -^".—Analysis  No.  378. 
— Normal  Mix:  Ellipse,  37%  ordinate  at  diam.  .10.5,  Tangent  to 
100%.— Per  Cent,  of  Cement,  10%. — Kind  Stone,  J.  P.— Kind  of 
Sand,  J.  P.— Date  Mixed,  Feb.  20.—  Date  Beam  Broken,  May  22. 
— Age  at  Break,  91  d. — Date  of  Coating,  May  23. — Age  at  Perm. 
Test,  112  d. — Dimensions  before  Coating,  5.91  X  5.95  X  18.0* 
— Hours  Soaked  before  Coating,  24. — Time  Yalve  Opened,  IO.45 


Times. 

Pressure. 

Water  passing, 
grams. 

Rate  of  flow  per 
minute,  grams. 

0 

20  lbs. 

0 

10 

“  “ 

0 1 

25 

40  “ 

or 

0  l 

29 

60  “ 

35 

60  “ 

61 

40 

t.  u 

98) 

45 

41  44 

103  V 

20 

50 

4  4  4  4 

99  | 

55 

80  41 

150 

60 

177) 

65 

189  V 

36 

168  ) 

Remarks. 


Pressure  increased  to  40  lbs. 
“  “  60  “ 
Water  appeared. 


Pressure  increased  to  80  lbs. 


General  Remarks 

?AJlLappear®d„after  pressure  Gf  20  lbs.  had  been  applied  for  10  minutes,  of  40 


n^Dutes  before  water1 appeared10'1^'  making  -creasing  pressures 

*This  measurement  is  assumed  to  be  18  inches 
surfac'e  was  roughened. 


Other  dimensions  taken  before 


Decrease  of  Permeability  with  Age. 

The  rate  of  flow  decreases  materially  with  age.  The  difference 
in  the  age  of  the  specimens  in  Table  16  is  not  sufficient  to  draw 
conclusions,  but  a  comparison  of  these  tests  with  those  in  Table  19, 
which  were  made  under  similar  conditions,  indicate  a  very  great 
reduction  in  the  flow  from  that  at  one  month,  to  that  at  three  and 
a  half  months. 


80 


Increase  of  Permeability  with  Pressure. 

By  a  comparison  in  Table  16  of  the  values  in  columns  19,  20  and 
21,  it  is  seen  that  the  rate  of  flow  increases  nearly  uniformly  with 
me  increase  of  pressure. 

Effect  of  Thickness  of  Concrete  Upon  Impermeability. 

The  data  given  in  Table  18  indicates  that  the  rate  of  flow  in¬ 
creases  as  the  thickness  of  the  concrete  decreases,  but  in  a  much 
larger  inverse  ratio.  All  of  the  tests  in  this  table  were  made  upon 
specimens  from  the  same  beam.  Column  4  gives  the  results  from  a 
regular  specimen  17  in.  in  length,  and  columns  2  and  3  the  re- 

TABLE  18. — Comparative  Permeability  of  Concrete  through  a 
Length  8.5  Inches  vs.  a  Length  17  Inches.  Specimen  No.  224. 

Cowe  Bay  Aggregates.  Proportions,  1:6.5  (by  Weight). 

Average  Age,  153  Days. 


1 

3  1 

3 

4 

5 

Pressure, 

lbs. 

Rate  of  Flow.  Grams  per  Minute. 

8.5"  X  5.95"  X  6.05"  specimens. 

17"  X  5.95"  X  6.15" 
specimen. 

(1) 

(2) 

Average. 

20 

0.16 

0.47 

0.32 

0 

40 

0.87 

1.49 

1.18 

0 

60 

1.40 

2.58 

1.99 

0 

80 

2.17 

3.93 

3.05 

0.47 

suits  from  two  specimens,  each  8|  inches  long,  from  the  same  beam. 
The  difference  in  the  permeability  of  1  and  2  is  greater  than  would 
be  expected  from  two  similar  specimens,  but  this  is  probably  ex¬ 
plained  by  differences  in  homogeneity  due  to  the  large  size  of  stone 
used  for  so  short  a  specimen,  and  to  the  fact  that  the  length  of*the 
two  pieces  which  were  broken  from  larger  ones  may  not  have  been 
absolutely  the  same.  Further  comparative  tests  of  similar  specimens 
are  evidently  required. 

Rate  of  Flow  During  a  Four-Hour  Period. 

A  specimen  subjected  to  continuous  uniform  pressure  for  a 
period  of  four  hours  shows  a  practically  uniform  rate  of  flow  during 
this  time.  The  results  are  shown  in  Table  19. 


81 


TABLE  19. — Uniformity  of  Rate  of  Flow  through  a  Specimen 
of  1  :  2.5: 6.5  (by  Weight).  Concrete  Specimen  No.  168. 

5.8  x  5.9  x  17.0  Inches  Long.  Jerome  Park 
Screenings  and  Stone.  Age,  119  Days. 


1 

2 

3 

4 

5 

Time,  hrs. 
min. 

Pressure,  lbs. 
per  sq.  in. 

Water 

passing, 

grams. 

Rate  of  flow 
per  minute, 
grams. 

Rate  of  flow 
per  hour, 
grams. 

0 

60 

0 

1.00 

kk 

446 

446 

1.05 

42 

8.4 

1.10 

44 

40 

8.0 

1.15 

fck 

41 

8.2 

2.00 

44 

344 

7.6 

467 

2.05 

44 

40 

8.0 

2.10 

44 

40 

8.0 

2.15 

44 

40 

8.0 

3.00 

lk 

338 

7.5 

458 

3.05 

44 

40 

8.0 

3.10 

44 

39 

7.8 

3.15 

40 

8.0 

4.00 

347 

1 

7.7 

466 

Comparative  Strength  of  Mortars  and  Permeability  of  Concretes 
with  Several  Sands  Available  at  Jerome  Park  Reservoir. 

At  one  period  of  the  construction  of  the  reservoir  the  quantity 
of  screenings  ran  low,  and  the  contractor  desired  to  use  instead  some 
very  fine  sand  which  was  available  on  the  reservoir  site.  Table  20 
shows  the  result  of  the  comparative  tests  of  strength  of  mortar  made 
at  the  suggestion  of  Mr.  F.  S.  Cook,  Division  Engineer,  with  several 
kinds  of  sand  and  with  Jerome  Park  screenings,  and  also  permea¬ 
bility  tests  of  concrete  in  proportions  1:2:5  by  volume  composed  of 
Giant  Portland  cement,  Jerome  Park  broken  stone,  and  the  same 
sands  used  in  tensile  tests.  The  tests  indicated  that  the  very  fine 
sand  gave  much  lower  strength  than  the  screenings,  and  that  mix¬ 
tures  of  the  screenings  and  fine  sand  in  equal  parts  gave  interme¬ 
diate  strengths. 

The  density  of  the  mortars  was  determined  by  the  regular  method 
adopted  in  the  laboratory,  and  the  values  of  the  quantity*  (  C  ^  ’ 

which  experiments  made  by  Mr.  R.  Feret  in  France  proved  to  be 
generally  in  direct  proportion  to  the  compressive  strength  of  the 
mortar,  occupy  nearly  similar  relative  positions  to  the  strength. 

The  results  of  these  tests  are  apparently  unexplainable  without 


c  =  absolute  volume  of  cement. 
s  —  absolute  volume  of  sand. 


TABLE  20.- Comparison  of  Sands  for  Strength,  Permeability,  and  Density  of  Concrete.  Tests  Made  to 
Determine  Availability  of  Sand  Found  at  Jerome  Park  Reservoir.  Giant  Cement.  Proportions  of 
Mortar,  1:2  by  Weight.  Proportions  of  Concrete,  1:2:5  by  Volume  *  Same  as  tn 


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>»  • 
gC? 

lO 

z  m 

2  | 

H  oi 

CO  . 

S3  + 

Ss 

S  o 
o£ 

a 

cu 

Ift- 

®  ^ 
S3 

® 

o 

5z  3 


S  I 


.gift  gft  gft  g 
ft  - 


ft  ft 

*-5  1-5 


:  [S  >*>43  43  +3  +3 

ft  :goqftft  ft  ft 


ft  q/  ft  ft  ft  ft 

»-5 


•sjaqxunu 

aouajajaH 


Based  on  a  unit  of  100  lb.  cement  per  cu.  ft. 


Fig.  23.  Apparatus  for  Volumetric  Tests  of  Density  of  Cement. 


I 


83 


further  experiments.  The  specimen  with  Jerome  Park  screenings  has 
substantially  the  same  permeability  as  the  specimens  Nos.  8  and  9, 
which  contain  very  fine  sand,  and  yet  the  strength  of  whose  mortars, 
as  would  naturally  be  expected  and  as  indicated  in  tests  2  and  3,  is 
extremely  low.  The  concrete  with  Cowe  Bay  sand,  specimen  7,  is 
less  permeable  than  specimen  6  with  Jerome  Park  screenings,  thus 
tending  to  confirm  the  results  of  the  regular  tests  in  Table  16.  For 
some  unexplained  reason  the  most  permeable  specimen  is  that  con¬ 
taining  a  combination  in  equal  parts  of  Jerome  Park  screenings 
and  one  of  the  fine  sands,  while  the  least  permeable  specimen  is  a 
combination  of  Jerome  Park  screenings  and  another  sand  which  is 
even  slightly  finer  than  the  former. 


Volumetric  Tests  of  Density  of  Neat  Cement  and  Mortar. 

During  the  progress  of  the  experiments  at  Jerome  Park  frequent 
tests  were  made  of  the  density  of  the  cement  which  was  being  used 
and  also  the  densities  of  various  mortars.  For  this  purpose  the 
cylinder  apparatus  described  for  the  density  experiment  upon  con¬ 
crete  was  used,  and  also  tests  were  made  upon  a  smaller  scale  with  a 
200  c.  c.  graduate  for  the  mold.  The  apparatus  used  for  these  tests 
on  the  small  scale  and  the  Jackson  specific  gravity  flask,  also  con¬ 
stantly  employed,  are  showm  in  Fig.  23. 


Effect  of  Different  Percentages  of  Water  Upon  Volume  and 
Density  of  Portland  Cement  Mortars  and  Concretes. 

Table  21  and  Fig.  24  illustrate  the  variation  in  volume  of 
paste  produced  from  the  same  weight  of  the  same  cement  with  differ¬ 
ent  percentages  of  water.  It  also  shows  the  difference  in  volume 
between  the  fresh  paste  as  mixed  and  the  same  paste  after  standing 
for  a  period  of  about  3  hours  and  compacting  by  occasional  shaking 
and  tapping  of  the  mold.  The  tests  were  made  in  the  graduates  as 
described  above.  By  adopting  a  standard  method  in  all  the  tests  and 
maintaining  a  uniform  consistency,  good  results  were  obtained. 
When  sand  is  mixed  with  the  cement,  there  is  much  less  variation 
in  the  volumes  of  the  mortars  due  to  different  percentages  of  water 


84 


than  in  neat  pastes,  but  the  variation  is  generally  very  appreciable, 
although  less  with  coarse  than  fine  sands. 


TABLE  21. _ Effect  of  Different  Percentages  of  Cement  upon 

the  Volume  of  Neat  Portland  Cement  Paste. 


1  1 

2  f 

3 

5 

6  !  7 

8 

9 

10 

11 

12 

Experiment  number. 

Nominal  mix. 

Kind  of  cement. 

•2  VOLUME  OF 

g  I  Paste. 

1  •  i 

Absolute  Volume. 

Weight  of  cement. 

Water  used  in  mixin 

Fresh. 

Final 

Compacted. 

Per  cent,  of  i 
mixing 

Fresh. 

Final 

compacted. 

Water. 

Cement 

(density). 

Water. 

Cement. 

(density). 

Grams. 

Grams. 

c.  c. 

c.  c. 

w. 

c. 

w. 

c. 

463 

Neat. 

Giant. 

300 

60 

20  165.8 

163.8 

.362 

.584 

.354 

.590 

464 

300 

69 

23  !  168.7 

167.7 

.391 

.546 

.404 

.574 

465 

u 

300 

78 

26  |  174.0 

172.3 

.438 

.543 

.441 

.560 

467 

u 

300 

96 

32  !  183.2 

179.3 

.504 

.508 

.508 

.534 

447 

tl 

300 

150 

50  244.0 

221.0 

.613 

.395 

.571 

.  435 

449 

300 

300 

100  390.6 

214.3 

.772 

.248 

.569 

.436 

The  resulting  volumes  of  different  concretes  of  the  same  materials 
and  proportions  but  with  varying  percentages  of  water  are  nearly 
constant  provided  sufficient  water  is  added  to  permit  thorough  com¬ 
pacting.  When  an  excess  of  water  is  used,  it  is  nearly  all  expelled 
as  the  solid  materials  settle  by  gravity.  There  is,  however,  a  slight 
variation  even  in  concrete.  A  dry  mixture,  provided  sufficient  water 
is  added  to  rise  to  the  top  on  hard  ramming,  can  be  compacted  some¬ 
what  more  than  a  concrete  of  medium  consistency,  while  a  very  wet 
concrete  is  apt  to  occupy  a  very  slightly  larger  volume  and  hence 
be  less  compact  than  a  medium  concrete.  In  most  cases  the  differ¬ 
ence  between  the  medium  and  very  wet  is  only  noticeable  by  ex¬ 
tremely  accurate  measurements. 


Tensile  Tests  of  Neat  Giant  Portland  Cement  Used  in  Concrete 

Beams,  1905. 

The  following  series  of  tests,  Table  22,  was  made  upon  the  cement 
which  was  used  in  the  beam  specimens. 


85 


TABLE  22. — Tensile  Strength  of  Neat  Giant  Portland  Cement 
Used  in  Concrete  Beams,  1905. 


First  Series. 


Date  tested. 

Age. 

! 

Average 
tensile 
strength, 
lb.  per  sq.  in. 

March 

7 . 

1  day 

252 

13 . 

7  days 

568 

April 

3 . 

4  weeks 

733 

May 

1 . 

8  “ 

760 

29 . 

12  “ 

733 

June 

26 . 

16  “ 

855 

July 

24 . 

20  “ 

774 

August  21 . 

24  “ 

746 

Second  Series. 


Date  Tested. 

Age. 

Average 
tensile 
strength, 
lb.  per  sq.  in. 

March 

23. . . . 

1  day 

218 

29  ... 

7  days 

556 

April 

19.... 

4  weeks. 

658 

May 

17.... 

8  “ 

686 

June 

14.... 

12  k‘ 

708 

July 

12. . . . 

16  “ 

656 

August 

9.... 

20  “ 

738 

September  6..  : 

24  “ 

754 

Note.— Each  value  is  an  average  of  5  briquettes. 


Mechanical  Analysis  of  Average  Jerome  Park  and  Cowe  Bay 
Materials  Used  in  Beam  Tests. 

The  figures  in  Tables  23  and  24  show  the  average  mechanical 
analyses  of  the  Jerome  Park  crushed  stone  and  screenings  and  the 
Cowe  Bay  gravel  and  sand  which  were  used  in  the  mixtures  made 
up  by  natural  proportions.  Each  of  these  analyses  is  an  average  of 
a  number  of  samples. 


TABLE  23.— Average  Analysis  of  Jerome  Park  Material. 


Sieve 

numbers. 

I 

Diameter  open- 
j  ing  in  sieves. 

2J4"  stone, 
per  cent, 
passing. 

2.25 

2.25 

100.0 

1.50 

1.50 

78.4 

1.00 

1.00 

41.8 

0.75 

.75 

29.9 

0.60 

.60 

18.4 

0.45 

.48 

11.4 

0.35 

.36 

6.8 

0.27 

.29 

3.6 

0.20 

.20 

1.9 

0.15 

.16 

1.3 

0.10 

.10 

1.0 

No.  10 

.075 

.67 

15 

.046 

.61 

20 

.034 

.58 

30 

.020 

.55 

40 

.016 

.48 

50 

.014 

.47 

74 

.0071 

.32 

100 

.0058  | 

.27 

150 

.0036 

.19 

200 

.0027  1 

.01 

1"  stone, 
per  cent, 
passing. 

J4”  stone, 
per  cent, 
passing. 

Screenings, 
per  cent, 
passing. 

100.0 

71.5 

44.2 

100.0 

27.3 

IOii.O 

99.7 

16.3 

59.6 

99.1 

8.6 

31.6 

96.9 

4.5 

16.7 

92.8 

3.1 

11.4 

87.2 

2.4 

8.7 

80.7 

1.6 

5.8 

76.7 

1.4 

5.3 

70.8 

1.39 

5.0 

66.3 

1.32 

4.8 

55.8 

1.15 

4.2 

47.8 

1.12 

4.1 

43.2 

0.76 

2.8 

21  0 

0.64 

2.3 

15.4 

0.45 

1.6 

6.7 

0.24 

0.8 

2.3 

86 


TABLE  24.  — Avebage  Analysis  of  Cowe  Bay  Sand  and  Stone. 


Sieve 

numbers. 

Diameter 
opening  in 
sieves. 

2J4”  stone, 
per  cent, 
passing. 

2.25 

2.25 

100.0 

1.50 

1.50 

94.2 

1.00 

1.00 

81.8 

0.75 

.75 

67.3 

0.60 

.60 

44.8 

0.45 

.48 

26.4 

0.35 

.36 

14.0 

0.27 

.29 

8.6 

0.20 

.20 

5.05 

0.15 

.16 

3.40 

0.10 

.10 

1.76 

No.  10 

.075 

1.57 

15 

.046 

1.38 

20 

.034 

1.28 

30 

.020 

1.09 

40 

.016 

0.98 

50 

.014 

0.80 

74 

.0071 

0.47 

100 

.0058 

0.43 

150 

.0036 

0.26 

200 

.0027 

0.01 

1”  stone, 

stone. 

Sand, 

per  cent. 

per  cent.  I 

per  cent. 

passing. 

passing.  | 

passing. 

100.0 

100.0 

100.00 

82.27 
54.77 

32.28 

100.0 

100.0 

97.9 

ioo.oo 

96.2 

17.12 

53.03 

95.0 

10.51 

32.57 

93.7 

6.17 

19.13 

W.8 

4.16 

12.88 

88.9 

2.15 

6.67 

1  85.1 

1 .92 

5.95 

78.9 

1.69 

5.23 

1  68.3 

1.56 

4.85 

i  62.4 

1.33 

4.13 

49.9 

1.20 

3.71 

37.3 

.98 

3.03 

1  31.8 

.57 

53 

1.78 

1.63 

7.1 

4.6 

.32 

.98 

2.3 

.01 

.04 

1.8 

Elasticity  Tests. 

Figs.  25  to  29  show  the  results  of  tests  of  elasticity  of  several  of 
the  capped  prisms.  These  tests  were  made  at  the  Stevens  Institute, 
Hoboken,  N.  J.  Headings  of  compressive  deformations  were  taken 
at  increments  corresponding  to  unit  increments  of  100  lb.,  and  m 
most  of  the  tests  the  load  was  released  at  500  and  1000  lb.  and  the 
permanent  set  recorded.  In  a  few  cases  shown  by  zigzag  lines  the 
effect  of  repeated  stress  was  also  measured.  The  results  are  tabu¬ 
lated  in  Table  25. 

Notice  in  the  diagram  that  nearly  all  the  curves  run  up  sharply 
from  100  lb.,  the  first  load  applied,  indicating  that  the  modulus 
between  100  and  200  lb.  is  not  greater  than  at  the  next  higher  load¬ 
ings.  After  deducting  the  set,  the  deformation  (shown  by  curve 
labelled  “Elastic”)  in  the  majority  of  the  specimens  at  first  in¬ 
creases  uniformly,  the  curve  being  in  these  cases  a  straight  line  m 
its  lower  portion.  The  point  of  tangency  with  the  decided  curve 
above  is  sometimes  considered  the  elastic  limit  of  the  concrete. 


HJL9N31  UNO  Nl  N0ISS3ydW0D 


APPLIED  LOADS  POUNDS  PER  SQUARE  INCH 

Fig.  27,-Total  and  Elastic  Compression  of  6-In.  by  6-In.  by  18-In.  Concrete  Prisms  Made  of  Giant  Portland  Cement  and  Cowe  Bay  Sand  and  Gravel. 

Average  Age,  about  140  Days, 


(1) 

©' 

© 

8 

© 

tM 

© 

tf 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 


92 


TABLE  25. — Modulus  of  Elasticity  of  Concrete  Prisms. 
Tests  for  deformation.  Jerome  Park  Reservoir.  1905. 


(2) 

(3) 

(4) 

(5) 

(6) 

(7) 

(8) 

(9) 

(10) 

(ID 

1 

(12) 

(13) 

Beam  number. 
(See  Table  14.) 

Proportions  by 
weight. 

Cement  to  total 
dry  material. 

Kind  of  stone. 

Kind  of  sand. 

Maximum  size 
of  stone. 

Uniformly 

graded  above 

diam. 

Per  cent,  finer 
than  diam. 

in  Col.  8. 

Density. 

Ultimate 

strength. 

Modulus  of 

elasticity. 

Modulus  taken 

between  limits. 

No. 

% 

In. 

In. 

% 

Lb.  per 

Lb.  p°r 

Lb.  per 

sq.  in. 

sq.  in. 

sq.  in. 

155A 

1:9 

10! 

Jerome 

Park. 

Jerome 

Park. 

j-2.25 

0.20 

37.8 

.855 

1  425 

2  143  000 

100-1  000 

151 A 

1:9 

10 

1.00 

0.10 

35.9 

.820 

1085 

1  702  000 

100-  500 

165A 

1:9 

10 

** 

0.50 

0.075 

36.3 

.770 

960 

1  436  000 

100-  500 

192A 

1:25:65 

10 

0.50 

Natural  Mix 

.773 

875 

1  274  000 

300—  500 

167 

1:3:6 

10 

2.25 

.812 

965 

2  425  000 

100-  500 

170A 

1:3:6 

10 

u 

64 

1.00 

.802 

860 

1  798  000 

100—  500 

176A 

1:3:6 

10 

0.50 

“ 

.772 

670 

878  000 

200-  500 

193A 

1:11 5 

8 

2.25 

0.20 

37.8 

.831 

940 

1  750  000 

100-  500 

155A  * 

1:9 

10 

2.25 

0.20 

37.8 

.855 

1  425 

2 143  000 

100—1  000 

179  A 

1:7 

12  y2 

2.25 

0.20 

37.8 

.852 

1  710 

2  250  000 

200—  800 

183A 

1:56T 

15 

u 

Cowe 

Bay. 

2.25 

0.20 

37.8 

.845 

1  920 

4  650  000 

100—  500 

234D 

1:8*  3 

10.6  j 

Cowe 

Bay. 

j-2.25 

0.20 

37.8 

.860 

1  800 

2  867  000 

100-1  500 

233 A 

1:1076 

8.5 

2.25 

0.20 

32.1 

.871 

940 

2  252  000 

100—  500 

217A 

1:843 

10.6 

2.25 

0.20 

32.1 

.855 

1880 

3  920  000 

100—  500 

22 4 A 

1:6s1 

13J4 

** 

2.25 

0.20 

32.1 

.865 

2  110 

3  675  000 

100—1  ooo 

225A 

1:530 

15.9 

2.25 

0.20 

32.1 

.867 

2  315 

4  273  000 

500-1  000 

221A 

1:281:562 

10.6 

2.25 

Natural  Mix 

.826 

1  455 

3  260  000 

100-  600 

227D 

1:281:562 

10.6 

1.00 

“ 

.832 

2  065 

3  100  000 

100-1  500 

213A 

1:850 

10.2  -j 

Jerome 

Park. 

Cowe 

Bay. 

[-2.25 

0.20 

I  33.8 

.873 

2  000 

3  480  000 

100-  :>00 

218A 

1:687 

12M 

2.25 

0.20 

1  33.8 

.866 

2150 

3  830  000 

100—  800 

216A 

1 :554 

15.3 

2.25 

0.20 

1  33.8 

.852 

2  440 

3  508  000 

200—1  600 

205A 

1:292:588 

10.2 

2.25 

Natural  Mix 

.831 

1  480 

3  037  000 

300-  500 

203A 

1:292:588 

10.2 

1.00 

.820 

1  555 

2  550  000 

100-  700 

207A 

1:292:588 

10.2 

46 

0.50 

.783 

1  145 

2  206  000 

100— 

*  Beam  155  repeated  here  to  facilitate  comparison. 


The  table  shows  several  interesting  comparisons: 

1.  — The  modulus  increases  with  the  maximum  size  of  stone. 
Compare  respectively  specimens  1,  2,  3,  5,  6,  7,  17,  18,  22,  23,  24. 

2.  — The  modulus  increases  with  the  percentage  of  cement.  Com¬ 
pare  respectively  8,  9,  10,  11,  13,  14,  15,  16,  19,  20,  21.  There  are 
one  or  two  exceptions  to  this  rule,  but  the  general  trend  is  unques¬ 
tionable. 

3.  — In  general  the  modulus  of  the  Cowe  Bay  gravel  and  sand  is 
higher  than  the  modulus  of  similar  specimens  mixed  with  Jerome 
Park  sand  and  screenings. 

4.  — The  modulus  of  specimens  with  mixture  of  Jerome  Park 
stone  and  Cowe  Bay  sand  is  in  general  slightly  lower  than  similar 
specimens  of  straight  Cowe  Bay  material. 


(T5507.) 


